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libpng/KNOWNBUG
2009-04-06 16:04:59 -05:00

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Known bugs and suggested enhancements in libpng-1.0.6
1. April 23, 2000 -- BUG -- binary incompatibility
Libpng-1.0.6 introduced binary incompatibility for applications that
make direct access to the info_ptr and png_ptr, due to the insertion
of the free_me member ahead of some previously existing members.
STATUS: Fixed in libpng-1.0.6g
2. April 15, 2000 -- BUG -- pnggccrd.c
If PNG_NO_GLOBAL_ARRAYS is defined, pnggccrd.c will not compile.
STATUS: Fixed in libpng-1.0.6g
3. April 1, 2000 -- BUG
Under some circumstances old applications that make direct access to
the info_ptr->text and its members might free the same memory that
is also free'ed by libpng during the png_destroy_struct process.
Fixed in libpng-1.0.6-patch-c and libpng-1.0.6d. The PNG_FREE_TEXT flag
bit in info_ptr->free_me is now checked to make sure libpng is responsible
for freeing the memory.
4. April 1, 2000 -- BUG
The non-ISO-C "strdup()" function is used in png.c
STATUS: The function has been simplified and no longer uses strdup()
in libpng-1.0.6-patch-c and libpng-1.0.6d.
5. March 24, 2000 -- BUG
The png_set_rgb_to_gray_fixed() function is setting incorrect weighting
factors.
STATUS: Fixed in libpng-1.0.6-patch-b and libpng-1.0.6d.
6. March 22, 2000 -- BUG
There are some printf() and fprintf() statements active in pngwutil.c
when PNG_NO_STDIO and PNG_sCAL_SUPPORTED are both defined.
STATUS: Fixed in libpng-1.0.6-patch-a and libpng-1.0.6d. The strcpy()
function is used instead.
7. March 22, 2000 -- BUG
The length of the iCCP chunk data is calculated incorrectly; because
it can contain zeroes, strlen() doesn't work.
STATUS: Fixed in libpng-1.0.6-patch-a and libpng-1.0.6d by adding a
data_length parameter to the png_decompress_chunk() function.
8. March 15, 1998 -- OPTIMIZATION -- Kevin Bracey
Loops need to be optimized everywhere
Make them count down instead of up -- Kevin Bracey
Optimizing compilers don't need this, and making
the change would be error prone -- Tom Lane, Glenn R-P
Question whether i-- or --i is better.
STATUS: Under investigation, postponed until after
libpng-1.1.0. About 160 loops will be turned around
in libpng-1.1.Nn, for testing.
9. July 4, 1998 -- ENHANCEMENT -- Glenn R-P
libpng-1.0.5 and earlier transform colors to gamma=1.0 space for
merging with background, and then back to the image's gamma. The
bit_depth of the intermediate (gamma=1.0) representation is probably
not sufficient. In the typical gamma=1/2.2 situation, the linear
pixels need about 4 more bits than the gamma-encoded ones, to avoid
loss of precision. A similar situation exists with the rgb_to_gray
operation.
STATUS: under development.
10. September 1999 -- ENHANCEMENT --
It should be possible to use libpng without floating-point aritmetic.
STATUS: Under investigation, implementation postponed until after
libpng-1.0.6. The application interface will change because replacements
for the png_set_gAMA(), png_set_cHRM(), and corresponding png_get_()
functions will be needed.
Much of this was completed in libpng-1.0.6, but gamma compensation
is not yet done in fixed-point arithmetic.