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Write compression options

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More sophisticated defaulting which helps significantly for some files along
with code to make it easier to control the compression defaults and to make the
settings honor the API calls the application makes (previously low windowBits
settings would get reset to higher values.)

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler
2016-02-02 05:58:38 -08:00
parent 5e88e9c396
commit af9ad9545d
6 changed files with 381 additions and 351 deletions
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33
pngwrite.c
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@@ -1021,38 +1021,7 @@ png_write_row(png_structrp png_ptr, png_const_bytep row)
/* Unlike the read code initialization happens automatically: */
if (row_number == 0 && pass == 0)
{
png_init_row_info(png_ptr); /* doesn't change row/pass/width */
# ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
/* If the app takes a png_info from a read operation and if the app
* has performed transforms on the data the png_info can contain
* IHDR information that cannot be represented in PNG. The code
* that writes the IHDR takes the color type from the
* png_info::format. The app adds transforms, before or after
* writing the IHDR, then the IHDR color_type stored in
* png_struct::color_type is used in png_init_row_info above to work
* out the actual row format.
*
* Prior to 1.7.0 this was not verified (there was no easy way to do
* so). Now we can check it here, however this is an:
*
* API CHANGE: in 1.7.0 an error may be flagged against bogus
* info_struct formats even though the app had removed them itself.
* It's just a warning at present.
*
* The test is that either the row_format produced by the write
* transforms exactly matches that in the original
* info_struct::format or that the info_struct::format was a simple
* mapping of the color_type that ended up in the IHDR:
*/
if (png_ptr->row_format != png_ptr->info_format &&
PNG_FORMAT_FROM_COLOR_TYPE(png_ptr->color_type) !=
png_ptr->info_format)
png_app_warning(png_ptr,
"info_struct format does not match IHDR");
# endif /* WRITE_TRANSFORMS */
}
png_write_start_IDAT(png_ptr); /* doesn't change row/pass/width */
else if (pass == 7U) /* too many calls; write already ended */
{