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Compression changes/fixes

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Simplified API: change handling of PNG_IMAGE_FLAG_FAST to use
PNG_COMPRESSION_HIGH_SPEED, and PNG_COMPRESSION_HIGH otherwise.

Compression: add missing break statements that caused some compression settings
to fall through to the 'HIGH' setting.

Internal: remove png_struct::flags, it only stored the 'library mismatch' flag
and that could never be accessed (because immediately after it was set the
png_struct, which was on the stack, was eliminated.)

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler
2016-06-08 08:37:20 -07:00
parent b70b51ba17
commit d52c8eba99
5 changed files with 29 additions and 56 deletions
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21
pngwrite.c
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@@ -1910,21 +1910,12 @@ png_image_write_main(png_voidp argument)
display->row_bytes = row_bytes;
}
/* Apply 'fast' options if the flag is set. */
if ((image->flags & PNG_IMAGE_FLAG_FAST) != 0)
{
# ifdef PNG_WRITE_FILTER_SUPPORTED
png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_NO_FILTERS);
# endif /* WRITE_FILTER */
/* NOTE: determined by experiment using pngstest, this reflects some
* balance between the time to write the image once and the time to read
* it about 50 times. The speed-up in pngstest was about 10-20% of the
* total (user) time on a heavily loaded system.
*/
# ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
png_set_compression_level(png_ptr, 3);
# endif /* WRITE_CUSTOMIZE_COMPRESSION */
}
/* Select the right compression mode based on the presence or absence of the
* 'fast' flag, this will use whatever options are available in the libpng
* build. It is always supported.
*/
png_set_compression(png_ptr, (image->flags & PNG_IMAGE_FLAG_FAST) != 0 ?
PNG_COMPRESSION_HIGH_SPEED : PNG_COMPRESSION_HIGH);
/* Check for the cases that currently require a pre-transform on the row
* before it is written. This only applies when the input is 16-bit and