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Imported from libpng-0.86.tar

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Guy Schalnat 1996-01-10 02:56:49 -06:00 committed by Glenn Randers-Pehrson
parent 6d76471acd
commit 69b1448f19
21 changed files with 572 additions and 410 deletions
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2
build.bat
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@ -1,2 +0,0 @@
make -fmakefile.bor -B -DMODEL=m %1 %2 %3 libpng >buildm.out
make -fmakefile.bor -B -DMODEL=l %1 %2 %3 libpng >buildl.out

62
example.c
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@ -79,13 +79,21 @@ void read_png(char *file_name)
png_info_init(info_ptr); png_info_init(info_ptr);
png_read_init(png_ptr); png_read_init(png_ptr);
/* set up the input control */ /* set up the input control if you are using standard C streams */
png_init_io(png_ptr, fp); png_init_io(png_ptr, fp);
/* read the file information */ /* if you are using replacement read functions, here you would call */
png_read_info(png_ptr, info_ptr); png_set_read_fn(png_ptr, (void *)io_ptr, user_read_fn);
/* where io_ptr is a structure you want available to the callbacks */
/* set up the transformations you want. Note that these are /* if you are using replacement message functions, here you would call */
png_set_message_fn(png_ptr, (void *)msg_ptr, user_error_fn, user_warning_fn);
/* where msg_ptr is a structure you want available to the callbacks */
/* read the file information */
png_read_info(png_ptr, info_ptr);
/* set up the transformations you want. Note that these are
all optional. Only call them if you want them */ all optional. Only call them if you want them */
/* expand paletted colors into true rgb */ /* expand paletted colors into true rgb */
@ -102,7 +110,7 @@ void read_png(char *file_name)
png_set_expand(png_ptr); png_set_expand(png_ptr);
/* Set the background color to draw transparent and alpha /* Set the background color to draw transparent and alpha
images over */ images over */
png_color_16 my_background; png_color_16 my_background;
if (info_ptr->valid & PNG_INFO_bKGD) if (info_ptr->valid & PNG_INFO_bKGD)
@ -120,7 +128,7 @@ void read_png(char *file_name)
/* tell libpng to strip 16 bit depth files down to 8 bits */ /* tell libpng to strip 16 bit depth files down to 8 bits */
if (info_ptr->bit_depth == 16) if (info_ptr->bit_depth == 16)
png_set_strip_16(png_ptr); png_set_strip_16(png_ptr);
/* dither rgb files down to 8 bit palettes & reduce palettes /* dither rgb files down to 8 bit palettes & reduce palettes
to the number of colors available on your screen */ to the number of colors available on your screen */
@ -138,7 +146,7 @@ void read_png(char *file_name)
png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS, png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
MAX_SCREEN_COLORS, NULL); MAX_SCREEN_COLORS, NULL);
} }
} }
/* invert monocrome files */ /* invert monocrome files */
if (info_ptr->bit_depth == 1 && if (info_ptr->bit_depth == 1 &&
@ -156,7 +164,7 @@ void read_png(char *file_name)
/* flip the rgb pixels to bgr */ /* flip the rgb pixels to bgr */
if (info_ptr->color_type == PNG_COLOR_TYPE_RGB || if (info_ptr->color_type == PNG_COLOR_TYPE_RGB ||
info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA) info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
png_set_bgr(png_ptr); png_set_bgr(png_ptr);
/* swap bytes of 16 bit files to least significant bit first */ /* swap bytes of 16 bit files to least significant bit first */
@ -174,7 +182,7 @@ void read_png(char *file_name)
else else
number_passes = 1; number_passes = 1;
/* optional call to update palette with transformations */ /* optional call to update palette with transformations */
png_start_read_image(png_ptr); png_start_read_image(png_ptr);
/* optional call to update the info structure */ /* optional call to update the info structure */
@ -192,7 +200,7 @@ void read_png(char *file_name)
for (pass = 0; pass < number_passes; pass++) for (pass = 0; pass < number_passes; pass++)
{ {
/* Read the image using the "sparkle" effect. */ /* Read the image using the "sparkle" effect. */
png_read_rows(png_ptr, row_pointers, NULL, number_of_rows); png_read_rows(png_ptr, row_pointers, NULL, number_of_rows);
/* If you are only reading on row at a time, this works */ /* If you are only reading on row at a time, this works */
for (y = 0; y < height; y++) for (y = 0; y < height; y++)
@ -210,7 +218,7 @@ void read_png(char *file_name)
/* read the rest of the file, getting any additional chunks /* read the rest of the file, getting any additional chunks
in info_ptr */ in info_ptr */
png_read_end(png_ptr, info_ptr); png_read_end(png_ptr, info_ptr);
/* clean up after the read, and free any memory allocated */ /* clean up after the read, and free any memory allocated */
png_read_destroy(png_ptr, info_ptr, (png_infop)0); png_read_destroy(png_ptr, info_ptr, (png_infop)0);
@ -262,7 +270,7 @@ initialize_png_reader()
function callbacks, even if you aren't using them all. function callbacks, even if you aren't using them all.
You can put a void pointer in place of the NULL, and You can put a void pointer in place of the NULL, and
retrieve the pointer from inside the callbacks using retrieve the pointer from inside the callbacks using
the function png_get_msg_ptr(png_ptr); */ the function png_get_progressive_ptr(png_ptr); */
png_set_progressive_read_fn(png_ptr, NULL, png_set_progressive_read_fn(png_ptr, NULL,
info_callback, row_callback, end_callback); info_callback, row_callback, end_callback);
@ -372,7 +380,7 @@ void write_png(char *file_name, ... other image information ...)
} }
/* set error handling */ /* set error handling */
if (setjmp(png_ptr->jmpbuf)) if (setjmp(png_ptr->jmpbuf))
{ {
png_write_destroy(png_ptr); png_write_destroy(png_ptr);
fclose(fp); fclose(fp);
@ -386,10 +394,18 @@ void write_png(char *file_name, ... other image information ...)
png_info_init(info_ptr); png_info_init(info_ptr);
png_write_init(png_ptr); png_write_init(png_ptr);
/* set up the output control */ /* set up the output control if you are using standard C streams */
png_init_io(png_ptr, fp); png_init_io(png_ptr, fp);
/* set the file information here */ /* if you are using replacement write functions, here you would call */
png_set_write_fn(png_ptr, (void *)io_ptr, user_write_fn, user_flush_fn);
/* where io_ptr is a structure you want available to the callbacks */
/* if you are using replacement message functions, here you would call */
png_set_message_fn(png_ptr, (void *)msg_ptr, user_error_fn, user_warning_fn);
/* where msg_ptr is a structure you want available to the callbacks */
/* set the file information here */
info_ptr->width = ; info_ptr->width = ;
info_ptr->height = ; info_ptr->height = ;
etc. etc.
@ -402,10 +418,18 @@ void write_png(char *file_name, ... other image information ...)
/* optional significant bit chunk */ /* optional significant bit chunk */
info_ptr->valid |= PNG_INFO_sBIT; info_ptr->valid |= PNG_INFO_sBIT;
info_ptr->sig_bit = true_bit_depth; /* if we are dealing with a grayscale image then */
info_ptr->sig_bit.gray = true_bit_depth;
/* optional gamma chunk */ /* otherwise, if we are dealing with a color image then */
info_ptr->valid |= PNG_INFO_gAMA; info_ptr->sig_bit.red = true_red_bit_depth;
info_ptr->sig_bit.green = true_green_bit_depth;
info_ptr->sig_bit.blue = true_blue_bit_depth;
/* if the image has an alpha channel then */
info_ptr->sig_bit.alpha = true_alpha_bit_depth;
/* optional gamma chunk is strongly suggested if you have any guess
as to the correct gamma of the image */
info_ptr->valid |= PNG_INFO_gAMA;
info_ptr->gamma = gamma; info_ptr->gamma = gamma;
/* other optional chunks */ /* other optional chunks */

492
libpng.txt
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@ -1,23 +1,29 @@
libpng.txt - a description on how to use and modify libpng libpng.txt - a description on how to use and modify libpng
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
Updated/rewritten per request in the libpng FAQ
Copyright (c) 1995 Frank J. T. Wojcik
December 18, 1995
I. Introduction
This file describes how to use and modify the PNG reference library This file describes how to use and modify the PNG reference library
(known as libpng) for your own use. There are four sections to this (known as libpng) for your own use. There are five sections to this
file: reading, writing, modifying, and configuration notes for various file: introduction, structures, reading, writing, and modification and
special platforms. Other then this file, the file example.c is a good configuration notes for various special platforms. Other then this
starting point for using the library, as it is heavily commented and file, example.c is a good starting point for using the library, as
should include everything most people will need. it is heavily commented and should include everything most people
will need.
Libpng was written as a companion to the PNG specification, as a Libpng was written as a companion to the PNG specification, as a
way to reduce the amount of time and effort it takes to support way to reduce the amount of time and effort it takes to support
the PNG file format in application programs. Most users will not the PNG file format in application programs. Most users will not
have to modify the library significantly; advanced users may want have to modify the library significantly; advanced users may want
to modify it more. The library was coded for both users. All to modify it more. The library was coded for both kind of users.
attempts were made to make it as complete as possible, while All attempts were made to make it as complete as possible, while
keeping the code easy to understand. Currently, this library keeping the code easy to understand. Currently, this library
only supports C. Support for other languages is being considered. only supports C. Support for other languages is being considered.
@ -31,16 +37,12 @@ majority of the needs of it's users.
Libpng uses zlib for its compression and decompression of PNG files. Libpng uses zlib for its compression and decompression of PNG files.
The zlib compression utility is a general purpose utility that is The zlib compression utility is a general purpose utility that is
useful for more then PNG files, and can be used without libpng for useful for more then PNG files, and can be used without libpng.
whatever use you want. See the documentation delivered with zlib for See the documentation delivered with zlib for more details.
more details.
Those people who do not need to modify libpng should still read at
least part of the PNG specification. The most important parts are
the data formats and the chunk descriptions. Those who will be
making changes to libpng should read the whole specification.
The structures:
II. Structures
There are two main structures that are important to libpng, png_struct There are two main structures that are important to libpng, png_struct
and png_info. The first, png_struct, is an internal structure that and png_info. The first, png_struct, is an internal structure that
@ -48,19 +50,24 @@ will not, for the most part, be used by the general user except as
the first variable passed to every png function call. the first variable passed to every png function call.
The png_info structure is designed to provide information about the The png_info structure is designed to provide information about the
png file. All of it's fields are intended to be examined or modified png file. All of its fields are intended to be examined or modified
by the user. See png.h for a good description of the png_info fields. by the user. See png.h for a good description of the png_info fields.
png.h is also an invaluable reference for programming with libpng.
And while I'm on the topic, make sure you include the png header file: And while I'm on the topic, make sure you include the png header file:
#include <png.h> #include <png.h>
III. Reading
Checking PNG files: Checking PNG files:
Libpng provides a simple check to see if a file is a png file. To Libpng provides a simple check to see if a file is a PNG file. To
use it, pass in the first 1 to 8 bytes of the file, and it will return use it, pass in the first 1 to 8 bytes of the file, and it will return
true or false (1 or 0) depending on whether the bytes could be part true or false (1 or 0) depending on whether the bytes could be part
of a png file. Of course, the more bytes you pass in, the greater of a PNG file. Of course, the more bytes you pass in, the greater
the accuracy of the prediction. If you pass in more then eight bytes, the accuracy of the prediction. If you pass in more then eight bytes,
libpng will only look at the first eight bytes. libpng will only look at the first eight bytes.
@ -69,14 +76,17 @@ libpng will only look at the first eight bytes.
Reading PNG files: Reading PNG files:
This section covers reading png files row by row. Progressive reading We'll now walk you through the possible functions to call when reading
is covered in the next section (although you still need to read this in a PNG file, briefly explaining the syntax and purpose of each one.
section, as much of the information is still needed). See example.c and png.h for more detail. While Progressive reading
is covered in the next section, you will still need some of the
functions discussed in this section to read a PNG file.
The first thing you need to do while reading a PNG file is to allocate The first thing you need to do while reading a PNG file, aside from
and initialize png_struct and png_info. As these are both large, you the standard I/O initialization, is to allocate and initialize
may not want to store these on the stack, unless you have stack space png_struct and png_info. As these are both large, you may not want to
to spare. Of course, you will want to check if malloc returns NULL. store these on the stack, unless you have stack space to spare. Of
course, you will want to check if malloc returns NULL.
png_structp png_ptr = malloc(sizeof (png_struct)); png_structp png_ptr = malloc(sizeof (png_struct));
if (!png_ptr) if (!png_ptr)
@ -100,6 +110,10 @@ much to undo.
return; return;
} }
If you are not using the standard i/o functions, you will need
to replace them with custom functions. See the discussion under
Customizing libpng.
After you have these structures, you will need to set up the After you have these structures, you will need to set up the
error handling. When libpng encounters an error, it expects to error handling. When libpng encounters an error, it expects to
longjmp back to your routine. Therefore, you will need to call longjmp back to your routine. Therefore, you will need to call
@ -108,8 +122,8 @@ read the file from different routines, you will need to update
the jmpbuf field every time you enter a new routine that will the jmpbuf field every time you enter a new routine that will
call a png_ function. See your documentation of setjmp/longjmp call a png_ function. See your documentation of setjmp/longjmp
for your compiler for more information on setjmp/longjmp. See for your compiler for more information on setjmp/longjmp. See
the discussion on png error handling in the Customizing Libpng the discussion on libpng error handling in the Customizing Libpng
section below for more information on the png error handling. section below for more information on the libpng error handling.
If an error occurs, and libpng longjmp's back to your setjmp, If an error occurs, and libpng longjmp's back to your setjmp,
you will want to call png_read_destroy() to free any memory. you will want to call png_read_destroy() to free any memory.
@ -123,7 +137,7 @@ you will want to call png_read_destroy() to free any memory.
return; return;
} }
Next, you will need to call png_read_init() and png_info_init(). Next, you will need to call png_info_init() and png_read_init().
These functions make sure all the fields are initialized to useful These functions make sure all the fields are initialized to useful
values, and, in the case of png_read_init(), and allocate any memory values, and, in the case of png_read_init(), and allocate any memory
needed for internal uses. You must call png_info_init() first, as needed for internal uses. You must call png_info_init() first, as
@ -132,7 +146,7 @@ the png_read_destroy() could try to png_free() random addresses, which
would be bad. would be bad.
png_info_init(info_ptr); png_info_init(info_ptr);
png_read_init(png_ptr); png_read_init(png_ptr);
Now you need to set up the input code. The default for libpng is Now you need to set up the input code. The default for libpng is
to use the C function fread(). If you use this, you will need to to use the C function fread(). If you use this, you will need to
@ -150,28 +164,44 @@ image data. You do this with a call to png_read_info().
The png_info structure is now filled in with all the data necessary The png_info structure is now filled in with all the data necessary
to read the file. Some of the more important parts of the png_info are: to read the file. Some of the more important parts of the png_info are:
width - holds the width of the file
height - holds the height of the file width - holds the width of the file
bit_depth - holds the bit depth of one of the image channels height - holds the height of the file
color_type - describes the channels and what they mean bit_depth - holds the bit depth of one of the image channels
see the PNG_COLOR_TYPE_ macros for more information color_type - describes the channels and what they mean
channels - number of channels of info for the color type (see the PNG_COLOR_TYPE_ macros for more information)
pixel_depth - bits per pixel channels - number of channels of info for the color type
rowbytes - number of bytes needed to hold a row pixel_depth - bits per pixel, the result of multiplying the bit_depth
times the channels
rowbytes - number of bytes needed to hold a row
interlace_type - currently 0 for none, 1 for interlaced interlace_type - currently 0 for none, 1 for interlaced
valid - this details which optional chunks were found in the file valid - this details which optional chunks were found in the
to see if a chunk was present, OR valid with the appropriate file to see if a chunk was present, AND valid with the
PNG_INFO_<chunk name> define. appropriate PNG_INFO_<chunk name> define.
palette and num_palette - the palette for the file
gamma - the gamma the file is written at These are also important, but their validity depends on whether a
sig_bit and sig_bit_number - the number of significant bits corresponding chunk exists. Use valid (see above) to ensure that what
trans, trans_values, and number_trans - transparency info you're doing with these values makes sense.
hist - histogram of palette
text and num_text - text comments in the file. palette - the palette for the file
num_palette - number of entries in the palette
gamma - the gamma the file is written at
sig_bit - the number of significant bits
for the gray, red, green, and blue channels, whichever are
appropriate for the given color type.
sig_bit_number - number of channels
trans_values - transparent pixel for non-paletted images
trans - array of transparent entries for paletted images
number_trans - number of transparent entries
hist - histogram of palette
text - text comments in the file.
num_text - number of comments
for more information, see the png_info definition in png.h and the for more information, see the png_info definition in png.h and the
PNG specification for chunk contents. Be careful with trusting PNG specification for chunk contents. Be careful with trusting
rowbytes, as some of the transformations could increase the space rowbytes, as some of the transformations could increase the space
needed to hold a row (expand, rgbx, xrgb, graph_to_rgb, etc.). needed to hold a row (expand, rgbx, xrgb, graph_to_rgb, etc.).
See png_update_info(), below.
A quick word about text and num_text. PNG stores comments in A quick word about text and num_text. PNG stores comments in
keyword/text pairs, one pair per chunk. While there are keyword/text pairs, one pair per chunk. While there are
@ -183,8 +213,8 @@ See the png specification for more details. There is no requirement
to have text after the keyword. to have text after the keyword.
Keywords are restricted to 80 characters without leading or trailing Keywords are restricted to 80 characters without leading or trailing
spaces, but spaces are allowed within the keyword Nothing spaces, but spaces are allowed within the keyword It is possible to
prevents you from duplicating the keyword. The text field is an have the same keyword any number of times. The text field is an
array of png_text structures, each holding pointer to a keyword array of png_text structures, each holding pointer to a keyword
and a pointer to a text string. Only the text string may be null. and a pointer to a text string. Only the text string may be null.
The keyword/text pairs are put into the array in the order that The keyword/text pairs are put into the array in the order that
@ -204,7 +234,7 @@ check to see if it has data that it can do somthing with, you should
make sure to only enable a transformation if it will be valid for make sure to only enable a transformation if it will be valid for
the data. For example, don't swap red and blue on grayscale data. the data. For example, don't swap red and blue on grayscale data.
This transforms bit depths of less then 8 to 8 bits, changes paletted This transforms bit depths of less than 8 to 8 bits, changes paletted
images to rgb, and adds an alpha channel if there is transparency images to rgb, and adds an alpha channel if there is transparency
information in a tRNS chunk. This is probably most useful on grayscale information in a tRNS chunk. This is probably most useful on grayscale
images with bit depths of 2 or 4 and tRNS chunks. images with bit depths of 2 or 4 and tRNS chunks.
@ -243,7 +273,8 @@ This handles gamma transformations of the data. Pass both the file
gamma and the desired screen gamma. If the file does not have a gamma and the desired screen gamma. If the file does not have a
gamma value, you can pass one anyway if you wish. Note that file gamma value, you can pass one anyway if you wish. Note that file
gammas are inverted from screen gammas. See the discussions on gammas are inverted from screen gammas. See the discussions on
gamma in the PNG specification for more information. gamma in the PNG specification for more information. It is strongly
recommended that viewers support gamma correction.
if (info_ptr->valid & PNG_INFO_gAMA) if (info_ptr->valid & PNG_INFO_gAMA)
png_set_gamma(png_ptr, screen_gamma, info_ptr->gamma); png_set_gamma(png_ptr, screen_gamma, info_ptr->gamma);
@ -256,16 +287,19 @@ PNG can have files with 16 bits per channel. If you only can handle
if (info_ptr->bit_depth == 16) if (info_ptr->bit_depth == 16)
png_set_strip_16(png_ptr); png_set_strip_16(png_ptr);
If you need to reduce an rgb file to a paletted file, or if a If you need to reduce an rgb file to a paletted file (perhaps because
paletted file has more entries then will fit on your screen, this a paletted file has more entries then will fit on your screen)
function will do that. Note that this is a simple match dither, that png_set_dither() will do that. Note that this is a simple match
merely finds the closest color available. This should work fairly dither, that merely finds the closest color available. This should
well with optimized palettes, and fairly badly with linear color work fairly well with optimized palettes, and fairly badly with linear
cubes. If you pass a palette that is larger then maximum_colors, color cubes. If you pass a palette that is larger then
the file will reduce the number of colors in the palette so it maximum_colors, the file will reduce the number of colors in the
will fit into maximum_colors. If there is an histogram, it will palette so it will fit into maximum_colors. If there is a histogram,
use it to make intelligent choises when reducing the palette. If it will use it to make intelligent choices when reducing the palette.
there is no histogram, it may not do a good job. If there is no histogram, it may not do as good a job.
This function will be rewritten and/or replaced in libpng 0.9, which
will have full two pass dithering with optimized palettes.
if (info_ptr->color_type & PNG_COLOR_MASK_COLOR) if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
{ {
@ -283,53 +317,54 @@ there is no histogram, it may not do a good job.
} }
} }
PNG files describe monocrome as black is zero and white is one. If you PNG files describe monocrome as black is zero and white is one. The
want this reversed (black is one and white is zero), call this: following code will reverse this (make black be one and white be zero):
if (info_ptr->bit_depth == 1 && if (info_ptr->bit_depth == 1 &&
info_ptr->color_type == PNG_COLOR_GRAY) info_ptr->color_type == PNG_COLOR_GRAY)
png_set_invert(png_ptr); png_set_invert(png_ptr);
PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. However, PNG files have possible bit depths of 1, 2, 4, 8, and 16. However,
they also provide a way to describe the true bit depth of the image. they also provide a way to describe the true bit depth of the image.
Then they require bits to be scaled to full range for the bit depth It is then required that values be "scaled" or "shifted" up to the bit
used in the file. If you want to reduce your pixels back down to depth used in the file. See the PNG specification for details. This
the true bit depth, call this: code reduces the pixels back down to the true bit depth:
if (info_ptr->valid & PNG_INFO_sBIT) if (info_ptr->valid & PNG_INFO_sBIT)
png_set_shift(png_ptr, &(info_ptr->sig_bit)); png_set_shift(png_ptr, &(info_ptr->sig_bit));
PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
they can, resulting in, for example, 8 pixels per byte for 1 bit files. they can, resulting in, for example, 8 pixels per byte for 1 bit
If you would rather these were expanded to 1 pixel per byte without files. This code expands to 1 pixel per byte without changing the
changing the values of the pixels, call this: values of the pixels:
if (info_ptr->bit_depth < 8) if (info_ptr->bit_depth < 8)
png_set_packing(png_ptr); png_set_packing(png_ptr);
PNG files store 3 color pixels in red, green, blue order. If you would PNG files store 3 color pixels in red, green, blue order. This code
rather have the pixels as blue, green, red, call this. changes the storage of the pixels to blue, green, red:
if (info_ptr->color_type == PNG_COLOR_TYPE_RGB || if (info_ptr->color_type == PNG_COLOR_TYPE_RGB ||
info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA) info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
png_set_bgr(png_ptr); png_set_bgr(png_ptr);
For some uses, you may want a grayscale image to be represented as For some uses, you may want a gray-scale image to be represented as
rgb. If you need this, call this: rgb. This code will do that conversion:
if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY || if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY ||
info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA) info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
png_set_gray_to_rgb(png_ptr); png_set_gray_to_rgb(png_ptr);
PNG files store 16 bit pixels in network byte order (most significant PNG files store 16 bit pixels in network byte order (big-endian,
bit first). If you would rather store them the other way, (the way ie. most significant bits first). This code chages the storage to the
PC's store them, for example), call this: other way (little-endian, ie. least significant bits first, eg. the
way PCs store them):
if (info_ptr->bit_depth == 16) if (info_ptr->bit_depth == 16)
png_set_swap(png_ptr); png_set_swap(png_ptr);
PNG files store rgb pixels packed into 3 bytes. If you would rather PNG files store rgb pixels packed into 3 bytes. This code packs them
pack them into 4 bytes, call this: into 4 bytes:
if (info_ptr->bit_depth == 8 && if (info_ptr->bit_depth == 8 &&
info_ptr->color_type == PNG_COLOR_TYPE_RGB) info_ptr->color_type == PNG_COLOR_TYPE_RGB)
@ -339,8 +374,8 @@ where filler_byte is the number to fill with, and the location is
either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
you want the filler before the rgb or after. you want the filler before the rgb or after.
Finally, if you need the interlacing as discussed below, call The last thing to handle is interlacing; this is covered in detail below,
this here: but you must call the function here.
if (info_ptr->interlace_type) if (info_ptr->interlace_type)
number_passes = png_set_interlace_handling(png_ptr); number_passes = png_set_interlace_handling(png_ptr);
@ -353,10 +388,10 @@ before it reads the first row.
png_start_read_image(png_ptr); png_start_read_image(png_ptr);
If you want, libpng will update your png_info structure to reflect libpng can update your png_info structure to reflect any
any transformations you've requested with this call. This is most transformations you've requested with this call. This is most useful
useful to update the info structures rowbytes field, so you can to update the info structures rowbytes field, so you can use it to
use it to allocate your image memory. This function calls allocate your image memory. This function calls
png_start_read_image(), so you don't have to call both of them. png_start_read_image(), so you don't have to call both of them.
png_read_update_info(png_ptr, info_ptr); png_read_update_info(png_ptr, info_ptr);
@ -391,31 +426,32 @@ If you don't want to read the whole image in at once, you can
use png_read_rows() instead. If there is no interlacing (check use png_read_rows() instead. If there is no interlacing (check
info_ptr->interlace_type), this is simple: info_ptr->interlace_type), this is simple:
png_read_rows(png_ptr, row_pointers, NULL, number_of_rows); png_read_rows(png_ptr, row_pointers, NULL, number_of_rows);
row_pointers is the same as in the png_read_image() call. row_pointers is the same as in the png_read_image() call.
If you are just calling one row at a time, you can do this for If you are just calling one row at a time, you can do this for
row_pointers: row_pointers:
png_bytep row_pointers = row; png_bytep row_pointers = row;
png_read_rows(png_ptr, &row_pointers, NULL, 1); png_read_rows(png_ptr, &row_pointers, NULL, 1);
When the file is interlaced (info_ptr->interlace_type == 1), things If the file is interlaced (info_ptr->interlace_type != 0), things get
get a good deal harder. PNG files have a complicated interlace scheme a good deal harder. The only currently (as of 12/95) defined
that breaks down an image into seven smaller images of varying size. interlacing scheme for PNG files (info_ptr->interlace_type == 1) is a
Libpng will fill out those images if you want, or it will give them complicated interlace scheme, known as Adam7, that breaks down an
to you "as is". If you want to fill them out, there is two ways image into seven smaller images of varying size. libpng will fill out
to do that. The one mentioned in the PNG specification is to expand those images or it will give them to you "as is". If you want to fill
each pixel to cover those pixels that have not been read yet. This them out, there are two ways to do that. The one mentioned in the PNG
results in a blocky image for the first pass, which gradually smooths specification is to expand each pixel to cover those pixels that have
out as more pixels are read. The other method is the "sparkle" method, not been read yet. This results in a blocky image for the first pass,
where pixels are draw only in their final locations, with the rest of which gradually smoothes out as more pixels are read. The other
the image remaining whatever colors they were initialized to before method is the "sparkle" method, where pixels are draw only in their
the start of the read. The first method usually looks better, but final locations, with the rest of the image remaining whatever colors
tends to be slower, as there are more pixels to put in the rows. Some they were initialized to before the start of the read. The first
examples to help clear this up: method usually looks better, but tends to be slower, as there are more
pixels to put in the rows.
If you don't want libpng to handle the interlacing details, just If you don't want libpng to handle the interlacing details, just
call png_read_rows() the correct number of times to read in all call png_read_rows() the correct number of times to read in all
@ -424,8 +460,8 @@ interlacing scheme.
If you want libpng to expand the images, call this above: If you want libpng to expand the images, call this above:
if (info_ptr->interlace_type) if (info_ptr->interlace_type)
number_passes = png_set_interlace_handling(png_ptr); number_passes = png_set_interlace_handling(png_ptr);
This will return the number of passes needed. Currently, this This will return the number of passes needed. Currently, this
is seven, but may change if another interlace type is added. is seven, but may change if another interlace type is added.
@ -452,7 +488,7 @@ If you only want the first effect (the rectangles), do the same as
before except pass the row buffer in the third parameter, and leave before except pass the row buffer in the third parameter, and leave
the second parameter NULL. the second parameter NULL.
png_read_rows(png_ptr, NULL, row_pointers, number_of_rows); png_read_rows(png_ptr, NULL, row_pointers, number_of_rows);
After you are finished reading the image, you can finish reading After you are finished reading the image, you can finish reading
the file. If you are interested in comments or time, you should the file. If you are interested in comments or time, you should
@ -513,10 +549,10 @@ initialize_png_reader()
/* this one's new. You will need to provide all three /* this one's new. You will need to provide all three
function callbacks, even if you aren't using them all. function callbacks, even if you aren't using them all.
You can put a void pointer in place of the NULL, and You can use any void pointer as the user_ptr, and
retrieve the pointer from inside the callbacks using retrieve the pointer from inside the callbacks using
the function png_get_progressive_ptr(png_ptr); */ the function png_get_progressive_ptr(png_ptr); */
png_set_progressive_read_fn(png_ptr, NULL, png_set_progressive_read_fn(png_ptr, user_ptr,
info_callback, row_callback, end_callback); info_callback, row_callback, end_callback);
return 0; return 0;
@ -597,11 +633,11 @@ end_callback(png_structp png_ptr, png_infop info)
} }
Writing PNG files: IV. Writing
Much of this is very similar to reading. However, everything of Much of this is very similar to reading. However, everything of
importance is repeated here, so you don't have to constantly look importance is repeated here, so you don't have to constantly look
back up in the Reading PNG files section to understand writing. back up in the reading section to understand writing.
The first thing you need to do while writing a PNG file is to allocate The first thing you need to do while writing a PNG file is to allocate
and initialize png_struct and png_info. As these are both large, you and initialize png_struct and png_info. As these are both large, you
@ -638,8 +674,8 @@ write the file from different routines, you will need to update
the jmpbuf field every time you enter a new routine that will the jmpbuf field every time you enter a new routine that will
call a png_ function. See your documentation of setjmp/longjmp call a png_ function. See your documentation of setjmp/longjmp
for your compiler for more information on setjmp/longjmp. See for your compiler for more information on setjmp/longjmp. See
the discussion on png error handling in the Customizing Libpng the discussion on libpng error handling in the Customizing Libpng
section below for more information on the png error handling. section below for more information on the libpng error handling.
if (setjmp(png_ptr->jmpbuf)) if (setjmp(png_ptr->jmpbuf))
{ {
@ -652,7 +688,7 @@ section below for more information on the png error handling.
return; return;
} }
Next, you will need to call png_write_init() and png_info_init(). Next, you will need to call png_info_init() and png_write_init().
These functions make sure all the fields are initialized to useful These functions make sure all the fields are initialized to useful
values, and, in the case of png_write_init(), allocate any memory values, and, in the case of png_write_init(), allocate any memory
needed for internal uses. Do png_info_init() first, so if needed for internal uses. Do png_info_init() first, so if
@ -660,7 +696,7 @@ png_write_init() longjmps, you know info_ptr is valid, so you
don't free random memory pointers, which would be bad. don't free random memory pointers, which would be bad.
png_info_init(info_ptr); png_info_init(info_ptr);
png_write_init(png_ptr); png_write_init(png_ptr);
Now you need to set up the input code. The default for libpng is Now you need to set up the input code. The default for libpng is
to use the C function fwrite(). If you use this, you will need to to use the C function fwrite(). If you use this, you will need to
@ -684,6 +720,7 @@ See the compression library for more details.
/* turn on or off filtering (1 or 0) */ /* turn on or off filtering (1 or 0) */
png_set_filtering(png_ptr, 1); png_set_filtering(png_ptr, 1);
/* compression level (0 - none, 6 - default, 9 - maximum) */
png_set_compression_level(png_ptr, Z_DEFAULT_COMPRESSION); png_set_compression_level(png_ptr, Z_DEFAULT_COMPRESSION);
png_set_compression_mem_level(png_ptr, 8); png_set_compression_mem_level(png_ptr, 8);
png_set_compression_strategy(png_ptr, Z_DEFAULT_STRATEGY); png_set_compression_strategy(png_ptr, Z_DEFAULT_STRATEGY);
@ -696,26 +733,36 @@ you are allowed to write after the image is the text chunks and the
time chunk. See png_write_end() for more information on that. If you time chunk. See png_write_end() for more information on that. If you
wish to write them before the image, fill them in now. If you want to wish to write them before the image, fill them in now. If you want to
wait until after the data, don't fill them until png_write_end(). For wait until after the data, don't fill them until png_write_end(). For
all the fields in png_info, see png.h. For explinations of what the all the fields in png_info, see png.h. For explanations of what the
fields contain, see the PNG specification. Some of the more important fields contain, see the PNG specification.
parts of the png_info are:
width - holds the width of the file Some of the more important parts of the png_info are:
height - holds the height of the file
bit_depth - holds the bit depth of one of the image channels width - holds the width of the file
color_type - describes the channels and what they mean height - holds the height of the file
see the PNG_COLOR_TYPE_ defines for more information bit_depth - holds the bit depth of one of the image channels
color_type - describes the channels and what they mean
see the PNG_COLOR_TYPE_ defines for more information
interlace_type - currently 0 for none, 1 for interlaced interlace_type - currently 0 for none, 1 for interlaced
valid - this describes which optional chunks to write to the valid - this describes which optional chunks to write to the
file. Note that if you are writing a PNG_COLOR_TYPE_PALETTE file. Note that if you are writing a
file, the PLTE chunk is not optional, but must still be marked PNG_COLOR_TYPE_PALETTE file, the PLTE chunk is not
for writing. To mark chunks for writing, OR valid with the optional, but must still be marked for writing. To
appropriate PNG_INFO_<chunk name> define. mark chunks for writing, OR valid with the appropriate
palette and num_palette - the palette for the file PNG_INFO_<chunk name> define.
gamma - the gamma the file is written at palette - the palette for the file
sig_bit and sig_bit_number - the number of significant bits num_palette - number of entries in the palette
trans, trans_values, and number_trans - transparency info gamma - the gamma the file is written at
hist - histogram of palette sig_bit - the number of significant bits
text and num_text - text comments in the file. for the gray, red, green, and blue channels, whichever are
appropriate for the given color type.
sig_bit_number - number of channels
trans_values - transparent pixel for non-paletted images
trans - array of transparent entries for paletted images
number_trans - number of transparent entries
hist - histogram of palette
text - text comments in the file.
num_text - number of comments
A quick word about text and num_text. text is an array of png_text A quick word about text and num_text. text is an array of png_text
structures. num_text is the number of valid structures in the array. structures. num_text is the number of valid structures in the array.
@ -751,7 +798,29 @@ time_t and png_convert_from_struct_tm() for struct tm. The
time_t routine uses gmtime(). You don't have to use either of time_t routine uses gmtime(). You don't have to use either of
these, but if you wish to fill in the png_time structure directly, these, but if you wish to fill in the png_time structure directly,
you should provide the time in universal time (GMT) if possible you should provide the time in universal time (GMT) if possible
instead of your local time. instead of your local time. Note that the year number is the full
year (ie 1996, rather than 96)
It is possible to have libpng flush any pending output, either manually,
or automatically after a certain number of lines have been written. To
flush the output stream a single time call:
png_write_flush(png_ptr);
and to have libpng flush the output stream periodically after a certain
number of scanlines have been written, call:
png_set_flush(png_ptr, nrows);
Note that the distance between rows is from the last time png_write_flush
was called, or the first row of the image if it has never been called.
So if you write 50 lines, and then png_set_flush 25, it will flush the
output on the next scanline, and on line 75, unless png_write_flush is
called earlier. If nrows is too small (less than about 10 lines) the
image compression may decrease dramatically (although this may be
acceptable for real-time applications). Infrequent flushing will only
degrade the compression performance by a few percent over images that
do not use flushing.
You are now ready to write all the file information up to the actual You are now ready to write all the file information up to the actual
image data. You do this with a call to png_write_info(). image data. You do this with a call to png_write_info().
@ -768,10 +837,10 @@ check to see if it has data that it can do somthing with, you should
make sure to only enable a transformation if it will be valid for make sure to only enable a transformation if it will be valid for
the data. For example, don't swap red and blue on grayscale data. the data. For example, don't swap red and blue on grayscale data.
PNG files store rgb pixels packed into 3 bytes. If you would rather PNG files store rgb pixels packed into 3 bytes. This code tells
supply the pixels as 4 bytes per pixel, call this: the library to use 4 bytes per pixel
png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
where the 0 is not used for writing, and the location is either where the 0 is not used for writing, and the location is either
PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether you PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether you
@ -779,10 +848,10 @@ want the filler before the rgb or after.
PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
they can, resulting in, for example, 8 pixels per byte for 1 bit files. they can, resulting in, for example, 8 pixels per byte for 1 bit files.
If you would rather supply the data 1 pixel per byte, but with the If the data is supplied at 1 pixel per byte, use this code, which will
values limited to the correct number of bits, call this: correctly pack the values:
png_set_packing(png_ptr); png_set_packing(png_ptr);
PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
data is of another bit depth, but is packed into the bytes correctly, data is of another bit depth, but is packed into the bytes correctly,
@ -790,13 +859,13 @@ this will scale the values to appear to be the correct bit depth.
Make sure you write a sBIT chunk when you do this, so others, if Make sure you write a sBIT chunk when you do this, so others, if
they want, can reduce the values down to their true depth. they want, can reduce the values down to their true depth.
/* do this before png_write_info() */ /* do this before png_write_info() */
info_ptr->valid |= PNG_INFO_sBIT; info_ptr->valid |= PNG_INFO_sBIT;
/* note that you can cheat and set all the values of /* note that you can cheat and set all the values of
sig_bit to true_bit_depth if you want */ sig_bit to true_bit_depth if you want */
if (info_ptr->color_type & PNG_COLOR_MASK_COLOR) if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
{ {
info_ptr->sig_bit.red = true_bit_depth; info_ptr->sig_bit.red = true_bit_depth;
info_ptr->sig_bit.green = true_bit_depth; info_ptr->sig_bit.green = true_bit_depth;
info_ptr->sig_bit.blue = true_bit_depth; info_ptr->sig_bit.blue = true_bit_depth;
@ -813,20 +882,21 @@ they want, can reduce the values down to their true depth.
png_set_shift(png_ptr, &(info_ptr->sig_bit)); png_set_shift(png_ptr, &(info_ptr->sig_bit));
PNG files store 16 bit pixels in network byte order (most significant PNG files store 16 bit pixels in network byte order (big-endian,
bit first). If you would rather supply them the other way, (the way ie. most significant bits first). This code would be used to supply
PC's store them, for example), call this: them the other way (little-endian, ie. least significant bits first,
eg. the way PCs store them):
png_set_swap(png_ptr); png_set_swap(png_ptr);
PNG files store 3 color pixels in red, green, blue order. If you would PNG files store 3 color pixels in red, green, blue order. This code
rather supply the pixels as blue, green, red, call this. would be used to supply the pixels as blue, green, red:
png_set_bgr(png_ptr); png_set_bgr(png_ptr);
PNG files describe moncrome as black is zero and white is one. If you PNG files describe monochrome as black being zero and white being
would rather supply the pixels with this reversed (black is one and one. This code would be used to supply the pixels with this reversed
white is zero), call this: (black being one and white being zero):
png_set_invert(png_ptr); png_set_invert(png_ptr);
@ -861,27 +931,29 @@ row_pointers:
png_write_rows(png_ptr, &row_pointers, 1); png_write_rows(png_ptr, &row_pointers, 1);
When the file is interlaced, things can get a good deal harder. When the file is interlaced, things can get a good deal more
PNG files have a complicated interlace scheme that breaks down an complicated. The only currently (as of 12/95) defined interlacing
image into seven smaller images of varying size. Libpng will scheme for PNG files is a compilcated interlace scheme, known as
build these images if you want, or you can do them yourself. If Adam7, that breaks down an image into seven smaller images of varying
you want to build them yourself, see the PNG specification for size. libpng will build these images for you, or you can do them
details of which pixels to write when. yourself. If you want to build them yourself, see the PNG
specification for details of which pixels to write when.
If you don't want libpng to handle the interlacing details, just If you don't want libpng to handle the interlacing details, just
call png_write_rows() the correct number of times to write all call png_write_rows() the correct number of times to write all
seven sub-images. seven sub-images.
If you want libpng to build the sub-images, call this: If you want libpng to build the sub-images, call this before you start
writing any rows:
number_passes = png_set_interlace_handling(png_ptr); number_passes = png_set_interlace_handling(png_ptr);
This will return the number of passes needed. Currently, this This will return the number of passes needed. Currently, this
is seven, but may change if another interlace type is added. is seven, but may change if another interlace type is added.
Then write the image number_passes times. Then write the image number_passes times.
png_write_rows(png_ptr, row_pointers, number_of_rows); png_write_rows(png_ptr, row_pointers, number_of_rows);
As some of these rows are not used, and thus return immediately, As some of these rows are not used, and thus return immediately,
you may want to read about interlacing in the PNG specification, you may want to read about interlacing in the PNG specification,
@ -906,7 +978,7 @@ read or write. For a more compact example of writing a PNG image,
see the file example.c. see the file example.c.
Customizing libpng: V. Modifying/Customizing libpng:
There are two issues here. The first is changing how libpng does There are two issues here. The first is changing how libpng does
standard things like memory allocation, input/output, and error handling. standard things like memory allocation, input/output, and error handling.
@ -916,21 +988,24 @@ adding new transformations, and generally changing how libpng works.
All of the memory allocation, input/output, and error handling in libpng All of the memory allocation, input/output, and error handling in libpng
goes through callbacks which are user setable. The default routines goes through callbacks which are user setable. The default routines
are in pngerror.c, pngmem.c, and pngio.c. To change these functions, are in pngerror.c, pngmem.c, and pngio.c. To change these functions,
call the approprate fn function. call the approprate _fn function.
Memory allocation is done through the functions png_large_malloc(), Memory allocation is done through the functions png_large_malloc(),
png_malloc(), png_realloc(), png_large_free(), and png_free(). png_malloc(), png_realloc(), png_large_free(), and png_free().
These currently just call the standard C functions. The large These currently just call the standard C functions. The large
functions must handle exactly 64K, but they don't have to handle functions must handle exactly 64K, but they don't have to handle
more then that. If your pointers can't access more then 64K at a more then that. If your pointers can't access more then 64K at a
time, you will want to set MAXSEG_64K in zlib.h. time, you will want to set MAXSEG_64K in zlib.h. Since it is unlikely
that the method of handling memory allocation on a platform will
change between applications, these functions must be modified in the
library at compile time.
Input/Output in libpng is done throught png_read() and png_write(), which Input/Output in libpng is done throught png_read() and png_write(), which
currently just call fread() and fwrite(). The FILE * is stored in currently just call fread() and fwrite(). The FILE * is stored in
png_struct, and is initialized via png_init_io(). If you wish to change png_struct, and is initialized via png_init_io(). If you wish to change
this, the library supplies callbacks that you can set through the the method of I/O, the library supplies callbacks that you can set through
function png_set_read_fn() and png_set_write_fn(). These functions the function png_set_read_fn() and png_set_write_fn() at run time. These
also provide a void pointer that can be retrieved via the function functions also provide a void pointer that can be retrieved via the function
png_get_io_ptr(). For example: png_get_io_ptr(). For example:
png_set_read_fn(png_structp png_ptr, voidp io_ptr, png_set_read_fn(png_structp png_ptr, voidp io_ptr,
@ -941,29 +1016,44 @@ png_get_io_ptr(). For example:
voidp io_ptr = png_get_io_ptr(png_ptr); voidp io_ptr = png_get_io_ptr(png_ptr);
The replacement I/O functions should have prototypes as follows:
void user_read_data(png_structp png_ptr, png_bytep data,
png_uint_32 length);
void user_write_data(png_structp png_ptr, png_bytep data,
png_uint_32 length);
void user_flush_data(png_structp png_ptr);
Note that you can pass NULL for the flush function if you are not doing Note that you can pass NULL for the flush function if you are not doing
flushing. flushing of the output data.
Error handling in libpng is done through png_error() and png_warning(). Error handling in libpng is done through png_error() and png_warning().
Errors handled through png_error() are fatal, meaning that png_error() Errors handled through png_error() are fatal, meaning that png_error()
should never return to it's caller. Currently, this is handled via should never return to it's caller. Currently, this is handled via
setjmp() and longjmp(), but you could change this to do things like setjmp() and longjmp(), but you could change this to do things like
exit() if you should wish. Similarly, both png_error() and png_warning() exit() if you should wish. On non-fatal errors, png_warning() is called
print a message on stderr, but that can also be changed. The motivation to print a warning message, and then control returns to the calling code.
behind using setjmp() and longjmp() is the C++ throw and catch exception By default png_error() and png_warning() print a message on stderr. If
handling methods. This makes the code much easier to write, as there you wish to change the behavior of the error functions, you will need to
is no need to check every return code of every function call. However, set up your own message callbacks. You do this like the I/O callbacks above.
there are some uncertainties about the status of local variables after
a longjmp, so the user may want to be careful about doing anything after png_set_message_fn(png_structp png_ptr, png_voidp msg_ptr,
png_msg_ptr error_fn, png_msg_ptr warning_fn);
png_voidp msg_ptr = png_get_msg_ptr(png_ptr);
The replacement message functions should have parameters as follows:
void user_error_fn(png_struct png_ptr, png_const_charp error_msg);
void user_warning_fn(png_struct png_ptr, png_const_charp warning_msg);
The motivation behind using setjmp() and longjmp() is the C++ throw and
catch exception handling methods. This makes the code much easier to write,
as there is no need to check every return code of every function call.
However, there are some uncertainties about the status of local variables
after a longjmp, so the user may want to be careful about doing anything after
setjmp returns non zero besides returning itself. Consult your compiler setjmp returns non zero besides returning itself. Consult your compiler
documentation for more details. If you wish to change this behavior, documentation for more details.
you will need to set up your own message callbacks. You do this like
the io callbacks above.
png_set_message_fn(png_structp png_ptr, png_voidp msg_ptr,
png_msg_ptr error_fn, png_msg_ptr warning_fn);
png_voidp msg_ptr = png_get_msg_ptr(png_ptr);
If you need to read or write custom chunks, you will need to get deeper If you need to read or write custom chunks, you will need to get deeper
into the libpng code. First, read the PNG specification, and have into the libpng code. First, read the PNG specification, and have
@ -983,7 +1073,7 @@ itself.
Configuring for 16 bit platforms: Configuring for 16 bit platforms:
You will may need to change the png_large_malloc() and You will probably need to change the png_large_malloc() and
png_large_free() routines in pngmem.c, as these are requred png_large_free() routines in pngmem.c, as these are requred
to allocate 64K. Also, you will want to look into zconf.h to tell to allocate 64K. Also, you will want to look into zconf.h to tell
zlib (and thus libpng) that it cannot allocate more then 64K at a zlib (and thus libpng) that it cannot allocate more then 64K at a
@ -993,8 +1083,8 @@ and libpng to 64K by defining MAXSEG_64K.
Configuring for Medium Model: Configuring for Medium Model:
Libpng's support for medium model has been tested on most of the popular Libpng's support for medium model has been tested on most of the popular
complers. Make sure MAXSEG_64K get's defined, USE_FAR_KEYWORD get's complers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
defined, and FAR get's defined to far in pngconf.h, and you should be defined, and FAR gets defined to far in pngconf.h, and you should be
all set. Everything in the library (except for zlib's structure) is all set. Everything in the library (except for zlib's structure) is
expecting far data. You must use the typedefs with the p or pp on expecting far data. You must use the typedefs with the p or pp on
the end for pointers (or at least look at them and be careful). Make the end for pointers (or at least look at them and be careful). Make
@ -1012,7 +1102,7 @@ memory allocators (png_malloc, etc.).
Configuring for compiler xxx: Configuring for compiler xxx:
All includes for libpng are in png.h. If you need to add/change/delete All includes for libpng are in pngconf.h. If you need to add/change/delete
an include, this is the place to do it. The includes that are not an include, this is the place to do it. The includes that are not
needed outside libpng are protected by the PNG_INTERNAL definition, needed outside libpng are protected by the PNG_INTERNAL definition,
which is only defined for those routines inside libpng itself. The which is only defined for those routines inside libpng itself. The
@ -1020,9 +1110,9 @@ files in libpng proper only include png.h.
Removing unwanted object code: Removing unwanted object code:
There are a bunch of #define's in png.h that control what parts of There are a bunch of #define's in pngconf.h that control what parts of
libpng are compiled. All the defines end in _SUPPORT. If you are libpng are compiled. All the defines end in _SUPPORT. If you are
not using an ability, you can change the #define to #undef and never going to use an ability, you can change the #define to #undef and
save yourself code and data space. All the reading and writing save yourself code and data space. All the reading and writing
specific code are in seperate files, so the linker should only grab specific code are in seperate files, so the linker should only grab
the files it needs. However, if you want to make sure, or if you the files it needs. However, if you want to make sure, or if you

10
png.c
View File

@ -1,10 +1,10 @@
/* png.c - location for general purpose png functions /* png.c - location for general purpose png functions
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL
@ -13,7 +13,7 @@
/* version information for c files. This better match the version /* version information for c files. This better match the version
string defined in png.h */ string defined in png.h */
char FARDATA png_libpng_ver[] = "0.85"; char FARDATA png_libpng_ver[] = "0.86";
/* place to hold the signiture string for a png file. */ /* place to hold the signiture string for a png file. */
png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10}; png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
@ -107,7 +107,7 @@ png_check_sig(png_bytep sig, int num)
voidpf voidpf
png_zalloc(voidpf png_ptr, uInt items, uInt size) png_zalloc(voidpf png_ptr, uInt items, uInt size)
{ {
voidp * ptr; voidp ptr;
ptr = ((voidp)png_large_malloc((png_structp)png_ptr, ptr = ((voidp)png_large_malloc((png_structp)png_ptr,
(png_uint_32)items * (png_uint_32)size)); (png_uint_32)items * (png_uint_32)size));

71
png.h
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@ -1,26 +1,33 @@
/* png.h - header file for png reference library /* png.h - header file for png reference library
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
December 19, 1995 Jan 10, 1996
Note: This is a beta version. It reads and writes valid files Note: This is a beta version. It reads and writes valid files
on the platforms I have, but it has had limited portability on the platforms I have, but it has had limited portability
testing. Furthermore, you will may have to modify the testing. Furthermore, you will may have to modify the
includes below to get it to work on your system, and you includes below to get it to work on your system, and you
may have to supply the correct compiler flags in the makefile. may have to supply the correct compiler flags in the makefile.
Read the readme.txt for more information, and how to contact Read the readme.txt for more information, and how to contact
me if you have any problems, or if you want your compiler/ me if you have any problems, or if you want your compiler/
platform to be supported in the next official libpng release. platform to be supported in the next official libpng release.
See readme.txt for more information See readme.txt for more information
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
Contributing Authors: Contributing Authors:
Andreas Dilger
Dave Martindale Dave Martindale
Guy Eric Schalnat Guy Eric Schalnat
Paul Schmidt Paul Schmidt
Tim Wegner Tim Wegner
The contributing authors would like to thank all those who helped
with testing, bug fixes, and patience. You know who you are. This
wouldn't have been possible without all of you.
Thanks to Frank J. T. Wojcik for reviewing the documentation
The PNG Reference Library is supplied "AS IS". The Contributing Authors The PNG Reference Library is supplied "AS IS". The Contributing Authors
and Group 42, Inc. disclaim all warranties, expressed or implied, and Group 42, Inc. disclaim all warranties, expressed or implied,
@ -67,10 +74,10 @@
/* version information for png.h - this should match the version /* version information for png.h - this should match the version
number in png.c */ number in png.c */
#define PNG_LIBPNG_VER_STRING "0.85" #define PNG_LIBPNG_VER_STRING "0.86"
/* careful here. I wanted to use 085, but that would be octal. Version /* careful here. I wanted to use 086, but that would be octal. Version
1.0 will be 100 here, etc. */ 1.0 will be 100 here, etc. */
#define PNG_LIBPNG_VER 85 #define PNG_LIBPNG_VER 86
/* variables defined in png.c - only it needs to define PNG_NO_EXTERN */ /* variables defined in png.c - only it needs to define PNG_NO_EXTERN */
#ifndef PNG_NO_EXTERN #ifndef PNG_NO_EXTERN
@ -265,6 +272,7 @@ typedef png_info FAR * FAR * png_infopp;
/* these determine if a function in the info needs freed */ /* these determine if a function in the info needs freed */
#define PNG_FREE_PALETTE 0x0001 #define PNG_FREE_PALETTE 0x0001
#define PNG_FREE_HIST 0x0002 #define PNG_FREE_HIST 0x0002
#define PNG_FREE_TRANS 0x0004
/* this is used for the transformation routines, as some of them /* this is used for the transformation routines, as some of them
change these values for the row. It also should enable using change these values for the row. It also should enable using
@ -290,10 +298,10 @@ typedef png_row_info FAR * FAR * png_row_infopp;
typedef struct png_struct_def png_struct; typedef struct png_struct_def png_struct;
typedef png_struct FAR * png_structp; typedef png_struct FAR * png_structp;
#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
typedef void (*png_msg_ptr) PNGARG((png_structp, png_const_charp)); typedef void (*png_msg_ptr) PNGARG((png_structp, png_const_charp));
typedef void (*png_rw_ptr) PNGARG((png_structp, png_bytep, png_uint_32)); typedef void (*png_rw_ptr) PNGARG((png_structp, png_bytep, png_uint_32));
typedef void (*png_flush_ptr) PNGARG((png_structp)); typedef void (*png_flush_ptr) PNGARG((png_structp));
#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
typedef void (*png_progressive_info_ptr) PNGARG((png_structp, png_infop)); typedef void (*png_progressive_info_ptr) PNGARG((png_structp, png_infop));
typedef void (*png_progressive_end_ptr) PNGARG((png_structp, png_infop)); typedef void (*png_progressive_end_ptr) PNGARG((png_structp, png_infop));
typedef void (*png_progressive_row_ptr) PNGARG((png_structp, png_bytep, typedef void (*png_progressive_row_ptr) PNGARG((png_structp, png_bytep,
@ -305,7 +313,7 @@ typedef void (*png_progressive_row_ptr) PNGARG((png_structp, png_bytep,
people who will be modifying the library for their own special needs. people who will be modifying the library for their own special needs.
*/ */
typedef struct png_struct_def struct png_struct_def
{ {
jmp_buf jmpbuf; /* used in png_error */ jmp_buf jmpbuf; /* used in png_error */
png_byte mode; /* used to determine where we are in the png file */ png_byte mode; /* used to determine where we are in the png file */
@ -507,6 +515,11 @@ extern void png_set_expand PNGARG((png_structp png_ptr));
extern void png_set_bgr PNGARG((png_structp png_ptr)); extern void png_set_bgr PNGARG((png_structp png_ptr));
#endif #endif
#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
/* Expand the grayscale to 24 bit RGB if necessary. */
extern void png_set_gray_to_rgb PNGARG((png_structp png_ptr));
#endif
#if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED) #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
#define PNG_FILLER_BEFORE 0 #define PNG_FILLER_BEFORE 0
#define PNG_FILLER_AFTER 1 #define PNG_FILLER_AFTER 1
@ -664,9 +677,10 @@ extern void png_set_compression_method PNGARG((png_structp png_ptr,
int method)); int method));
/* These next functions are stubs of typical c functions for input/output, /* These next functions are stubs of typical c functions for input/output,
memory, and error handling. They are in the file pngstub.c, and are memory, and error handling. They are in the file pngio.c, and pngerror.c.
set up to be easily modified for users that need to. See the file These functions can be replaced at run time for those applications that
pngstub.c for more information */ need to handle I/O in a different manner. See the file libpng.txt for
more information */
/* Write the data to whatever output you are using. */ /* Write the data to whatever output you are using. */
extern void png_write_data PNGARG((png_structp png_ptr, png_bytep data, extern void png_write_data PNGARG((png_structp png_ptr, png_bytep data,
@ -676,7 +690,7 @@ extern void png_write_data PNGARG((png_structp png_ptr, png_bytep data,
extern void png_read_data PNGARG((png_structp png_ptr, png_bytep data, extern void png_read_data PNGARG((png_structp png_ptr, png_bytep data,
png_uint_32 length)); png_uint_32 length));
/* Initialize the input/output for the png file. */ /* Initialize the input/output for the png file to the default functions. */
extern void png_init_io PNGARG((png_structp png_ptr, FILE *fp)); extern void png_init_io PNGARG((png_structp png_ptr, FILE *fp));
/* Replace the error message and abort, and warning functions with user /* Replace the error message and abort, and warning functions with user
@ -691,7 +705,7 @@ extern png_voidp png_get_msg_ptr PNGARG((png_structp png_ptr));
/* Replace the default data output functions with a user supplied one(s). /* Replace the default data output functions with a user supplied one(s).
If buffered output is not used, then output_flush_fn can be set to NULL. If buffered output is not used, then output_flush_fn can be set to NULL.
if PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile time If PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile time
output_flush_fn will be ignored (and thus can be NULL). */ output_flush_fn will be ignored (and thus can be NULL). */
extern void png_set_write_fn PNGARG((png_structp png_ptr, png_voidp io_ptr, extern void png_set_write_fn PNGARG((png_structp png_ptr, png_voidp io_ptr,
png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)); png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn));
@ -709,7 +723,7 @@ extern void png_set_push_fn PNGARG((png_structp png_ptr, png_voidp push_ptr,
png_progressive_end_ptr end_fn)); png_progressive_end_ptr end_fn));
/* returns the user pointer assiciated with the push read functions */ /* returns the user pointer assiciated with the push read functions */
extern void * png_get_progressive_ptr PNGARG((png_structp png_ptr)); extern png_voidp png_get_progressive_ptr PNGARG((png_structp png_ptr));
extern png_voidp png_large_malloc PNGARG((png_structp png_ptr, extern png_voidp png_large_malloc PNGARG((png_structp png_ptr,
png_uint_32 size)); png_uint_32 size));
@ -1118,6 +1132,9 @@ extern void png_do_unshift PNGARG((png_row_infop row_info, png_bytep row,
extern void png_do_invert PNGARG((png_row_infop row_info, png_bytep row)); extern void png_do_invert PNGARG((png_row_infop row_info, png_bytep row));
#endif #endif
extern void png_build_grayscale_palette PNGARG((int bit_depth,
png_colorp palette));
#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED) #if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
extern void png_do_gray_to_rgb PNGARG((png_row_infop row_info, extern void png_do_gray_to_rgb PNGARG((png_row_infop row_info,
png_bytep row)); png_bytep row));

3
pngchang.txt
View File

@ -62,5 +62,8 @@ version 0.85
added i/o, error, and memory callback functions added i/o, error, and memory callback functions
fixed some bugs (16 bit, 4 bit interlaced, etc.) fixed some bugs (16 bit, 4 bit interlaced, etc.)
added first run progressive reader (barely tested) added first run progressive reader (barely tested)
version 0.86
fixed bugs
improved documentation

6
pngconf.h
View File

@ -1,10 +1,10 @@
/* pngconf.c - machine configurable file for libpng /* pngconf.c - machine configurable file for libpng
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
/* Any machine specific code is near the front of this file, so if you /* Any machine specific code is near the front of this file, so if you

39
pngerror.c
View File

@ -1,21 +1,23 @@
/* pngerror.c - stub functions for i/o and memory allocation /* pngerror.c - stub functions for i/o and memory allocation
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
This file provides a location for all error handling. Users which This file provides a location for all error handling. Users which
need special error handling are expected to modify the code in this need special error handling are expected to write replacement functions
file to meet their needs. See the instructions at each function. */ and use png_set_message_fn() to use those functions. See the instructions
at each function. */
#define PNG_INTERNAL #define PNG_INTERNAL
#include "png.h" #include "png.h"
/* This function is called whenever there is an error. Replace with /* This function is called whenever there is a fatal error. This function
however you wish to handle the error. Note that this function should not be changed. If there is a need to handle errors differently,
MUST NOT return, or the program will crash */ you should supply a replacement error function and use png_set_message_fn()
to replace the error function at run-time. */
void void
png_error(png_structp png_ptr, png_const_charp message) png_error(png_structp png_ptr, png_const_charp message)
{ {
@ -27,6 +29,10 @@ png_error(png_structp png_ptr, png_const_charp message)
png_default_error(png_ptr, message); png_default_error(png_ptr, message);
} }
/* This function is called whenever there is a non-fatal error. This function
should not be changed. If there is a need to handle warnings differently,
you should supply a replacement warning function and use
png_set_message_fn() to replace the warning function at run-time. */
void void
png_warning(png_structp png_ptr, png_const_charp message) png_warning(png_structp png_ptr, png_const_charp message)
{ {
@ -54,11 +60,10 @@ png_default_error(png_structp png_ptr, png_const_charp message)
#endif #endif
} }
/* This function is called when there is a warning, but the library /* This function is called when there is a warning, but the library thinks
thinks it can continue anyway. You don't have to do anything here it can continue anyway. Replacement functions don't have to do anything
if you don't want to. In the default configuration, png_ptr is here if you don't want to. In the default configuration, png_ptr is
not used, but it is passed in case it may be useful. */ not used, but it is passed in case it may be useful. */
void void
png_default_warning(png_structp png_ptr, png_const_charp message) png_default_warning(png_structp png_ptr, png_const_charp message)
{ {
@ -70,10 +75,10 @@ png_default_warning(png_structp png_ptr, png_const_charp message)
#endif #endif
} }
/* This function is called when the application wants to use another /* This function is called when the application wants to use another method
method of handling errors and warnings. Note that the error function must of handling errors and warnings. Note that the error function MUST NOT
NOT return to the calling routine or serious problems will occur. The return to the calling routine or serious problems will occur. The error
error return method used in the default routine calls return method used in the default routine calls
longjmp(png_ptr->jmpbuf, 1) */ longjmp(png_ptr->jmpbuf, 1) */
void void
png_set_message_fn(png_structp png_ptr, png_voidp msg_ptr, png_msg_ptr error_fn, png_set_message_fn(png_structp png_ptr, png_voidp msg_ptr, png_msg_ptr error_fn,

59
pngio.c
View File

@ -1,10 +1,10 @@
/* pngstub.c - stub functions for i/o and memory allocation /* pngio.c - stub functions for i/o and memory allocation
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
This file provides a location for all input/output. Users which need This file provides a location for all input/output. Users which need
special handling are expected to write functions which have the same special handling are expected to write functions which have the same
@ -16,13 +16,12 @@
#define PNG_INTERNAL #define PNG_INTERNAL
#include "png.h" #include "png.h"
/* Write the data to whatever output you are using. The default /* Write the data to whatever output you are using. The default routine
routine writes to a file pointer. If you need to write to something writes to a file pointer. Note that this routine sometimes gets called
else, this is a good example of how to do it. Note that this routine with very small lengths, so you should implement some kind of simple
sometimes gets called with very small lengths, so you should implement buffering if you are using unbuffered writes. This should never be asked
some kind of simple buffering if you are using unbuffered writes. This to write more then 64K on a 16 bit machine. The cast to png_size_t is
should never be asked to write more then 64K on a 16 bit machine. The there to quiet warnings of certain compilers. */
cast to png_size_t is there for insurance. */
void void
png_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length) png_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
@ -33,6 +32,10 @@ png_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
png_error(png_ptr, "Call to NULL write function"); png_error(png_ptr, "Call to NULL write function");
} }
/* This is the function which does the actual writing of data. If you are
not writing to a standard C stream, you should create a replacement
write_data function and use it at run time with png_set_write_fn(), rather
than changing the library. */
#ifndef USE_FAR_KEYWORD #ifndef USE_FAR_KEYWORD
void void
png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length) png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
@ -106,17 +109,12 @@ png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
#endif #endif
/* Read the data from whatever input you are using. The default /* Read the data from whatever input you are using. The default routine
routine reads from a file pointer. If you need to read from something reads from a file pointer. Note that this routine sometimes gets called
else, this is the place to do it. We suggest saving the old code with very small lengths, so you should implement some kind of simple
for future use. Note that this routine sometimes gets called with buffering if you are using unbuffered reads. This should never be asked
very small lengths, so you should implement some kind of simple to read more then 64K on a 16 bit machine. The cast to png_size_t is
buffering if you are using unbuffered reads. This should there to quiet some compilers */
never be asked to read more then 64K on a 16 bit machine. The cast
to png_size_t is there for insurance, but if you are having problems
with it, you can take it out. Just be sure to cast length to whatever
fread needs in that spot if you don't have a function prototype for
it. */
void void
png_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length) png_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
{ {
@ -135,6 +133,10 @@ png_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
} }
} }
/* This is the function which does the actual reading of data. If you are
not reading from a standard C stream, you should create a replacement
read_data function and use it at run time with png_set_read_fn(), rather
than changing the library. */
#ifndef USE_FAR_KEYWORD #ifndef USE_FAR_KEYWORD
void void
png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length) png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
@ -221,7 +223,7 @@ png_default_flush(png_struct *png_ptr)
arguments a pointer to a png_struct, a pointer to arguments a pointer to a png_struct, a pointer to
data to be written, and a 32-bit unsigned int which is data to be written, and a 32-bit unsigned int which is
the number of bytes to be written. The new write the number of bytes to be written. The new write
function should call (*(png_ptr->error_fn))("Error msg") function should call png_error("Error msg")
to exit and output any fatal error messages. to exit and output any fatal error messages.
flush_data_fn - pointer to a new flush function which takes as its flush_data_fn - pointer to a new flush function which takes as its
arguments a pointer to a png_struct. After a call to arguments a pointer to a png_struct. After a call to
@ -264,7 +266,9 @@ png_set_write_fn(png_structp png_ptr, png_voidp io_ptr, png_rw_ptr write_data_fn
read_data_fn - pointer to a new input function which takes as it's read_data_fn - pointer to a new input function which takes as it's
arguments a pointer to a png_struct, a pointer to arguments a pointer to a png_struct, a pointer to
a location where input data can be stored, and a 32-bit a location where input data can be stored, and a 32-bit
unsigned int which is the number of bytes to be read. */ unsigned int which is the number of bytes to be read.
To exit and output any fatal error messages the new write
function should call png_error(png_ptr, "Error msg"). */
void void
png_set_read_fn(png_struct *png_ptr, void *io_ptr, png_rw_ptr read_data_fn) png_set_read_fn(png_struct *png_ptr, void *io_ptr, png_rw_ptr read_data_fn)
{ {
@ -293,10 +297,9 @@ png_get_io_ptr(png_struct *png_ptr)
return png_ptr->io_ptr; return png_ptr->io_ptr;
} }
/* Initialize the input/output for the png file. If you change /* Initialize the default input/output functions for the png file. If you
the read and write routines, you will probably need to change change the read, or write routines, you can call either png_set_read_fn()
this routine (or write your own). If you change the parameters or png_set_write_fn() instead of png_init_io(). */
of this routine, remember to change png.h also. */
void void
png_init_io(png_structp png_ptr, FILE *fp) png_init_io(png_structp png_ptr, FILE *fp)
{ {

6
pngmem.c
View File

@ -1,10 +1,10 @@
/* pngmem.c - stub functions for memory allocation /* pngmem.c - stub functions for memory allocation
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
This file provides a location for all memory allocation. Users which This file provides a location for all memory allocation. Users which
need special memory handling are expected to modify the code in this file need special memory handling are expected to modify the code in this file

19
pngpread.c
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@ -1,10 +1,10 @@
/* pngpread.c - read a png file in push mode /* pngpread.c - read a png file in push mode
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL
@ -850,8 +850,10 @@ png_push_read_text(png_structp png_ptr, png_infop info)
text_size = png_ptr->buffer_size; text_size = png_ptr->buffer_size;
else else
text_size = png_ptr->current_text_left; text_size = png_ptr->current_text_left;
png_push_fill_buffer(png_ptr, png_ptr->current_text_ptr, text_size); png_push_fill_buffer(png_ptr, (png_bytep)png_ptr->current_text_ptr,
png_calculate_crc(png_ptr, png_ptr->current_text_ptr, text_size); text_size);
png_calculate_crc(png_ptr, (png_bytep)png_ptr->current_text_ptr,
text_size);
png_ptr->current_text_left -= text_size; png_ptr->current_text_left -= text_size;
png_ptr->current_text_ptr += text_size; png_ptr->current_text_ptr += text_size;
} }
@ -902,8 +904,10 @@ png_push_read_ztxt(png_structp png_ptr, png_infop info)
text_size = png_ptr->buffer_size; text_size = png_ptr->buffer_size;
else else
text_size = png_ptr->current_text_left; text_size = png_ptr->current_text_left;
png_push_fill_buffer(png_ptr, png_ptr->current_text_ptr, text_size); png_push_fill_buffer(png_ptr, (png_bytep)png_ptr->current_text_ptr,
png_calculate_crc(png_ptr, png_ptr->current_text_ptr, text_size); text_size);
png_calculate_crc(png_ptr, (png_bytep)png_ptr->current_text_ptr,
text_size);
png_ptr->current_text_left -= text_size; png_ptr->current_text_left -= text_size;
png_ptr->current_text_ptr += text_size; png_ptr->current_text_ptr += text_size;
} }
@ -950,6 +954,7 @@ png_push_read_ztxt(png_structp png_ptr, png_infop info)
key_size = text - key; key_size = text - key;
text_size = 0; text_size = 0;
text = NULL; text = NULL;
ret = Z_STREAM_END;
while (png_ptr->zstream->avail_in) while (png_ptr->zstream->avail_in)
{ {

6
pngrcb.c
View File

@ -1,9 +1,9 @@
/* pngrcb.c - callbacks while reading a png file /* pngrcb.c - callbacks while reading a png file
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL

8
pngread.c
View File

@ -1,10 +1,10 @@
/* pngread.c - read a png file /* pngread.c - read a png file
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL
@ -633,7 +633,7 @@ png_read_destroy(png_structp png_ptr, png_infop info, png_infop end_info)
if (png_ptr->do_free & PNG_FREE_PALETTE) if (png_ptr->do_free & PNG_FREE_PALETTE)
png_free(png_ptr, info->palette); png_free(png_ptr, info->palette);
#if defined(PNG_READ_BACKGROUND_SUPPORTED) && defined(PNG_READ_bKGD_SUPPORTED) #if defined(PNG_READ_BACKGROUND_SUPPORTED) && defined(PNG_READ_bKGD_SUPPORTED)
if (png_ptr->do_free & PNG_FREE_PALETTE) if (png_ptr->do_free & PNG_FREE_TRANS)
png_free(png_ptr, info->trans); png_free(png_ptr, info->trans);
#endif #endif
#if defined(PNG_READ_hIST_SUPPORTED) #if defined(PNG_READ_hIST_SUPPORTED)

63
pngrtran.c
View File

@ -1,10 +1,10 @@
/* pngrtran.c - transforms the data in a row for png readers /* pngrtran.c - transforms the data in a row for png readers
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL
@ -1168,7 +1168,8 @@ png_build_grayscale_palette(int bit_depth, png_colorp palette)
color_inc = 1; color_inc = 1;
break; break;
default: default:
num_palette = 0; num_palette = 0;
color_inc = 0;
break; break;
} }
@ -1493,11 +1494,11 @@ png_do_background(png_row_infop row_info, png_bytep row,
else else
{ {
v = gamma_16[ v = gamma_16[
*(sp + 1) >> gamma_shift][*sp]; *(sp + 1) >> gamma_shift][*sp];
*sp = (v >> 8) & 0xff; *sp = (v >> 8) & 0xff;
*(sp + 1) = v & 0xff; *(sp + 1) = v & 0xff;
} }
} }
} }
else else
#endif #endif
@ -2025,7 +2026,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
you do this after you deal with the trasparency issue on grayscale you do this after you deal with the trasparency issue on grayscale
or rgb images. If your bit depth is 8, use gamma_table, if it is 16, or rgb images. If your bit depth is 8, use gamma_table, if it is 16,
use gamma_16_table and gamma_shift. Build these with use gamma_16_table and gamma_shift. Build these with
build_gamma_table(). If your bit depth < 8, gamma correct a build_gamma_table(). If your bit depth <= 8, gamma correct a
palette, not the data. */ palette, not the data. */
void void
png_do_gamma(png_row_infop row_info, png_bytep row, png_do_gamma(png_row_infop row_info, png_bytep row,
@ -2659,7 +2660,7 @@ png_build_gamma_table(png_structp png_ptr)
if ((int)png_ptr->sig_bit.green > sig_bit) if ((int)png_ptr->sig_bit.green > sig_bit)
sig_bit = png_ptr->sig_bit.green; sig_bit = png_ptr->sig_bit.green;
if ((int)png_ptr->sig_bit.blue > sig_bit) if ((int)png_ptr->sig_bit.blue > sig_bit)
sig_bit = png_ptr->sig_bit.blue; sig_bit = png_ptr->sig_bit.blue;
} }
else else
{ {
@ -2691,17 +2692,17 @@ png_build_gamma_table(png_structp png_ptr)
png_ptr->gamma_16_table = (png_uint_16pp)png_malloc(png_ptr, png_ptr->gamma_16_table = (png_uint_16pp)png_malloc(png_ptr,
num * sizeof (png_uint_16p )); num * sizeof (png_uint_16p ));
if ((png_ptr->transformations & PNG_16_TO_8) && if ((png_ptr->transformations & PNG_16_TO_8) &&
!(png_ptr->transformations & PNG_BACKGROUND)) !(png_ptr->transformations & PNG_BACKGROUND))
{ {
double fin, fout; double fin, fout;
png_uint_32 last, max; png_uint_32 last, max;
for (i = 0; i < num; i++) for (i = 0; i < num; i++)
{ {
png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr, png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr,
256 * sizeof (png_uint_16)); 256 * sizeof (png_uint_16));
} }
g = 1.0 / g; g = 1.0 / g;
last = 0; last = 0;
@ -2709,33 +2710,33 @@ png_build_gamma_table(png_structp png_ptr)
{ {
fout = ((double)i + 0.5) / 256.0; fout = ((double)i + 0.5) / 256.0;
fin = pow(fout, g); fin = pow(fout, g);
max = (png_uint_32)(fin * (double)(num << 8)); max = (png_uint_32)(fin * (double)((png_uint_32)num << 8));
while (last <= max) while (last <= max)
{ {
png_ptr->gamma_16_table[(int)(last & 0xff) >> shift] png_ptr->gamma_16_table[(int)(last & (0xff >> shift))]
[(int)(last >> (8 - shift))] = [(int)(last >> (8 - shift))] =
(png_uint_16)i | ((png_uint_16)i << 8); (png_uint_16)i | ((png_uint_16)i << 8);
last++; last++;
} }
} }
while (last < ((png_uint_32)num << 8)) while (last < ((png_uint_32)num << 8))
{ {
png_ptr->gamma_16_table[(int)(last & 0xff) >> shift] png_ptr->gamma_16_table[(int)(last & (0xff >> shift))]
[(int)(last >> (8 - shift))] = [(int)(last >> (8 - shift))] =
(png_uint_16)65535L; (png_uint_16)65535L;
last++; last++;
} }
} }
else else
{ {
for (i = 0; i < num; i++) for (i = 0; i < num; i++)
{ {
png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr, png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr,
256 * sizeof (png_uint_16)); 256 * sizeof (png_uint_16));
ig = (((png_uint_32)i * ig = (((png_uint_32)i *
(png_uint_32)png_gamma_shift[shift]) >> 4); (png_uint_32)png_gamma_shift[shift]) >> 4);
for (j = 0; j < 256; j++) for (j = 0; j < 256; j++)
{ {
png_ptr->gamma_16_table[i][j] = png_ptr->gamma_16_table[i][j] =
(png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) / (png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) /

92
pngrutil.c
View File

@ -1,10 +1,10 @@
/* pngrutil.c - utilities to read a png file /* pngrutil.c - utilities to read a png file
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL
@ -164,7 +164,8 @@ png_handle_PLTE(png_structp png_ptr, png_infop info, png_uint_32 length)
num = (int)length / 3; num = (int)length / 3;
palette = (png_colorp)png_malloc(png_ptr, num * sizeof (png_color)); palette = (png_colorp)png_malloc(png_ptr, num * sizeof (png_color));
for (i = 0; i < num; i++) png_ptr->do_free |= PNG_FREE_PALETTE;
for (i = 0; i < num; i++)
{ {
png_byte buf[3]; png_byte buf[3];
@ -189,7 +190,8 @@ png_handle_gAMA(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != 4) if (length != 4)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect gAMA chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
@ -210,7 +212,9 @@ void
png_handle_sBIT(png_structp png_ptr, png_infop info, png_uint_32 length) png_handle_sBIT(png_structp png_ptr, png_infop info, png_uint_32 length)
{ {
int slen; int slen;
png_byte buf[4]; png_byte buf[4];
buf[0] = buf[1] = buf[2] = buf[3] = 0;
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
slen = 3; slen = 3;
@ -219,8 +223,9 @@ png_handle_sBIT(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != (png_uint_32)slen) if (length != (png_uint_32)slen)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect sBIT chunk length");
return; png_crc_skip(png_ptr, length);
return;
} }
png_crc_read(png_ptr, buf, length); png_crc_read(png_ptr, buf, length);
@ -250,7 +255,8 @@ png_handle_cHRM(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != 32) if (length != 32)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect cHRM chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
@ -299,12 +305,14 @@ png_handle_tRNS(png_structp png_ptr, png_infop info, png_uint_32 length)
{ {
if (length > png_ptr->num_palette) if (length > png_ptr->num_palette)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect tRNS chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
png_ptr->trans = (png_bytep)png_malloc(png_ptr, length); png_ptr->trans = (png_bytep)png_malloc(png_ptr, length);
png_crc_read(png_ptr, png_ptr->trans, length); png_ptr->do_free |= PNG_FREE_TRANS;
png_crc_read(png_ptr, png_ptr->trans, length);
png_ptr->num_trans = (int)length; png_ptr->num_trans = (int)length;
} }
else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB) else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
@ -313,7 +321,8 @@ png_handle_tRNS(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != 6) if (length != 6)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect tRNS chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
@ -329,16 +338,17 @@ png_handle_tRNS(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != 2) if (length != 2)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect tRNS chunk length");
return; png_crc_skip(png_ptr, length);
} return;
}
png_crc_read(png_ptr, buf, 2); png_crc_read(png_ptr, buf, 2);
png_ptr->num_trans = 1; png_ptr->num_trans = 1;
png_ptr->trans_values.gray = png_get_uint_16(buf); png_ptr->trans_values.gray = png_get_uint_16(buf);
} }
else else
png_error(png_ptr, "Invalid tRNS chunk"); png_warning(png_ptr, "Invalid tRNS chunk");
png_read_tRNS(png_ptr, info, png_ptr->trans, png_ptr->num_trans, png_read_tRNS(png_ptr, info, png_ptr->trans, png_ptr->num_trans,
&(png_ptr->trans_values)); &(png_ptr->trans_values));
@ -361,7 +371,8 @@ png_handle_bKGD(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != (png_uint_32)truelen) if (length != (png_uint_32)truelen)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect bKGD chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
@ -385,18 +396,20 @@ png_handle_bKGD(png_structp png_ptr, png_infop info, png_uint_32 length)
void void
png_handle_hIST(png_structp png_ptr, png_infop info, png_uint_32 length) png_handle_hIST(png_structp png_ptr, png_infop info, png_uint_32 length)
{ {
int num, i; int num, i;
if (length != 2 * png_ptr->num_palette) if (length != 2 * png_ptr->num_palette)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect hIST chunk length");
return; png_crc_skip(png_ptr, length);
} return;
}
num = (int)length / 2; num = (int)length / 2;
png_ptr->hist = (png_uint_16p)png_malloc(png_ptr, png_ptr->hist = (png_uint_16p)png_malloc(png_ptr,
num * sizeof (png_uint_16)); num * sizeof (png_uint_16));
for (i = 0; i < num; i++) png_ptr->do_free |= PNG_FREE_HIST;
for (i = 0; i < num; i++)
{ {
png_byte buf[2]; png_byte buf[2];
@ -417,7 +430,8 @@ png_handle_pHYs(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != 9) if (length != 9)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect pHYs chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
@ -440,11 +454,12 @@ png_handle_oFFs(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != 9) if (length != 9)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect oFFs chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
png_crc_read(png_ptr, buf, 9); png_crc_read(png_ptr, buf, 9);
offset_x = png_get_uint_32(buf); offset_x = png_get_uint_32(buf);
offset_y = png_get_uint_32(buf + 4); offset_y = png_get_uint_32(buf + 4);
@ -462,7 +477,8 @@ png_handle_tIME(png_structp png_ptr, png_infop info, png_uint_32 length)
if (length != 7) if (length != 7)
{ {
png_crc_skip(png_ptr, length); png_warning(png_ptr, "Incorrect tIME chunk length");
png_crc_skip(png_ptr, length);
return; return;
} }
@ -525,7 +541,8 @@ png_handle_zTXt(png_structp png_ptr, png_infop info, png_uint_32 length)
/* zTXt can't have zero text */ /* zTXt can't have zero text */
if (text == key + (png_size_t)length) if (text == key + (png_size_t)length)
{ {
png_large_free(png_ptr, key); png_warning(png_ptr, "Zero length zTXt chunk");
png_large_free(png_ptr, key);
return; return;
} }
@ -546,13 +563,18 @@ png_handle_zTXt(png_structp png_ptr, png_infop info, png_uint_32 length)
key_size = text - key; key_size = text - key;
text_size = 0; text_size = 0;
text = NULL; text = NULL;
ret = Z_STREAM_END;
while (png_ptr->zstream->avail_in) while (png_ptr->zstream->avail_in)
{ {
ret = inflate(png_ptr->zstream, Z_PARTIAL_FLUSH); ret = inflate(png_ptr->zstream, Z_PARTIAL_FLUSH);
if (ret != Z_OK && ret != Z_STREAM_END) if (ret != Z_OK && ret != Z_STREAM_END)
{ {
if (png_ptr->zstream->msg)
png_warning(png_ptr, png_ptr->zstream->msg);
else
png_warning(png_ptr, "zTXt decompression error");
inflateReset(png_ptr->zstream); inflateReset(png_ptr->zstream);
png_ptr->zstream->avail_in = 0; png_ptr->zstream->avail_in = 0;
png_large_free(png_ptr, key); png_large_free(png_ptr, key);

6
pngtest.c
View File

@ -1,9 +1,9 @@
/* pngtest.c - a simple test program to test libpng /* pngtest.c - a simple test program to test libpng
libpng 1.0 beta 2 - version 0.81 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
August 24, 1995 January 10, 1996
*/ */
#include <stdio.h> #include <stdio.h>

6
pngtrans.c
View File

@ -2,10 +2,10 @@
/* pngtrans.c - transforms the data in a row /* pngtrans.c - transforms the data in a row
routines used by both readers and writers routines used by both readers and writers
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL

8
pngwrite.c
View File

@ -1,10 +1,10 @@
/* pngwrite.c - general routines to write a png file /* pngwrite.c - general routines to write a png file
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
/* get internal access to png.h */ /* get internal access to png.h */
@ -114,7 +114,7 @@ png_write_info(png_structp png_ptr, png_infop info)
void void
png_write_end(png_structp png_ptr, png_infop info) png_write_end(png_structp png_ptr, png_infop info)
{ {
/* see if user wants us to write information chunks */ /* see if user wants us to write information chunks */
if (info) if (info)
{ {
#if defined(PNG_WRITE_tIME_SUPPORTED) #if defined(PNG_WRITE_tIME_SUPPORTED)

6
pngwtran.c
View File

@ -1,10 +1,10 @@
/* pngwtran.c - transforms the data in a row for png writers /* pngwtran.c - transforms the data in a row for png writers
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL

6
pngwutil.c
View File

@ -1,10 +1,10 @@
/* pngwutil.c - utilities to write a png file /* pngwutil.c - utilities to write a png file
libpng 1.0 beta 2 - version 0.85 libpng 1.0 beta 2 - version 0.86
For conditions of distribution and use, see copyright notice in png.h For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc. Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
December 19, 1995 January 10, 1996
*/ */
#define PNG_INTERNAL #define PNG_INTERNAL
#include "png.h" #include "png.h"

12
readme.txt
View File

@ -1,12 +1,8 @@
readme.txt - for libpng 0.85 readme.txt - for libpng 0.86
This is a bug fix for the second beta version of libpng 1.0, and This is a bug fix for the second beta version of libpng 1.0, and
a first try at a progressive (push) reader. It hasn't been a first try at a progressive (push) reader. It hasn't been
tested very much, but I'm not going to have time to test it for tested as much as the pull reader, but seems to work ok.
a few days, and I wanted to give an advanced look at the
progressive reader to everyone. Please report bugs back
(and fixes, if you find them), and I'll release a new version
in a week or two. Thanks.
I've implemented the callback functions for the error/warning I've implemented the callback functions for the error/warning
messages and the input/output. See the libpng.txt messages and the input/output. See the libpng.txt
@ -44,8 +40,7 @@ be available at the same place you picked up libpng. If it is
not there, try ftp.uu.net in the /graphics/png directory. not there, try ftp.uu.net in the /graphics/png directory.
This code is currently being archived at ftp.uu.net in the This code is currently being archived at ftp.uu.net in the
/graphics/png directory, and at ftp.group42.com (204.94.158.25) /graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT)
in the /pub/png directory, and on CompuServe, Lib 20 (PNG SUPPORT)
at GO GRAPHSUP. If you can't find it in any of those places, at GO GRAPHSUP. If you can't find it in any of those places,
e-mail me, and I'll help you find it. e-mail me, and I'll help you find it.
@ -87,5 +82,4 @@ Good luck, and happy coding.
Internet: schalnat@group42.com Internet: schalnat@group42.com
CompuServe: 75501,1625 CompuServe: 75501,1625
Web: www.group42.com Web: www.group42.com
FTP: ftp.group42.com (204.94.158.25)