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[master] Improved the optimization of the zlib CMF byte

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(see libpng-1.2.6beta03).
This commit is contained in:
Glenn Randers-Pehrson
2011-04-06 07:07:42 -05:00
parent 2053a26873
commit 28534bd47a
3 changed files with 26 additions and 3 deletions
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8
ANNOUNCE
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@@ -1,5 +1,5 @@
Libpng 1.4.6rc02 - April 3, 2011 Libpng 1.4.6rc02 - April 6, 2011
This is not intended to be a public release. It will be replaced This is not intended to be a public release. It will be replaced
within a few weeks by a public version or by another test version. within a few weeks by a public version or by another test version.
@@ -67,7 +67,11 @@ version 1.4.6beta07 [March 22, 2011]
Fixed a bug (present since libpng-1.0.7) that makes png_handle_sPLT() fail Fixed a bug (present since libpng-1.0.7) that makes png_handle_sPLT() fail
to compile when PNG_NO_POINTER_INDEXING is defined (Chubanov Kirill) to compile when PNG_NO_POINTER_INDEXING is defined (Chubanov Kirill)
version 1.4.6rc01 [April 3, 2011] version 1.4.6rc01 [March 31, 2011]
No changes.
version 1.4.6rc02 [April 6, 2011]
Improved the optimization of the zlib CMF byte (see libpng-1.2.6beta03).
Send comments/corrections/commendations to glennrp at users.sourceforge.net Send comments/corrections/commendations to glennrp at users.sourceforge.net
or to png-mng-implement at lists.sf.net (subscription required; visit or to png-mng-implement at lists.sf.net (subscription required; visit

6
CHANGES
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@@ -2779,7 +2779,11 @@ version 1.4.6beta07 [March 22, 2011]
Fixed a bug (present since libpng-1.0.7) that makes png_handle_sPLT() fail Fixed a bug (present since libpng-1.0.7) that makes png_handle_sPLT() fail
to compile when PNG_NO_POINTER_INDEXING is defined (Chubanov Kirill) to compile when PNG_NO_POINTER_INDEXING is defined (Chubanov Kirill)
version 1.4.6rc01 [April 3, 2011] version 1.4.6rc01 [March 31, 2011]
No changes.
version 1.4.6rc02 [April 6, 2011]
Improved the optimization of the zlib CMF byte (see libpng-1.2.6beta03).
Send comments/corrections/commendations to glennrp at users.sourceforge.net Send comments/corrections/commendations to glennrp at users.sourceforge.net
or to png-mng-implement at lists.sf.net (subscription required; visit or to png-mng-implement at lists.sf.net (subscription required; visit

15
pngwutil.c
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@@ -682,9 +682,24 @@ png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
if (length >= 2 && if (length >= 2 &&
png_ptr->height < 16384 && png_ptr->width < 16384) png_ptr->height < 16384 && png_ptr->width < 16384)
{ {
/* Compute the maximum possible length of the datastream */
/* Number of pixels, plus for each row a filter byte and possible
* and possibly a padding byte, so increase the maximum
* size to account for these.
*/
png_uint_32 uncompressed_idat_size = png_ptr->height * png_uint_32 uncompressed_idat_size = png_ptr->height *
((png_ptr->width * ((png_ptr->width *
png_ptr->channels * png_ptr->bit_depth + 15) >> 3); png_ptr->channels * png_ptr->bit_depth + 15) >> 3);
/* If it's interlaced, each block of 8 rows is sent as up to
* 14 rows, i.e., 6 additional rows, each with a filter byte
* and possibly a padding byte
*/
if (png_ptr->interlaced)
uncompressed_idat_size += ((png_ptr->height + 7)/8) *
(png_ptr->bit_depth < 8 ? 12 : 6);
unsigned int z_cinfo = z_cmf >> 4; unsigned int z_cinfo = z_cmf >> 4;
unsigned int half_z_window_size = 1 << (z_cinfo + 7); unsigned int half_z_window_size = 1 << (z_cinfo + 7);
while (uncompressed_idat_size <= half_z_window_size && while (uncompressed_idat_size <= half_z_window_size &&