zlib filtering PNGs
Posted: 2019-09-25T20:45:20-07:00
Hi guys
I am writing some code to improve the compression of PNGs and I am having some difficulties with PNGs that have been edited with the GIMP (as JPEGs) and then transformed into PNGs on the fly by Perl Magick.
Essentially, if I turn on Z_FILTERED in the compression code the PNGs will not display, though a casual look over them in a hex editor reveals no problem.
If Z_DEFAULT is used then there is no problem... sorry to be vague about this but I really don't know why this happens and wonder if anyone could give me some clues to what might be up?
Uyen
I am writing some code to improve the compression of PNGs and I am having some difficulties with PNGs that have been edited with the GIMP (as JPEGs) and then transformed into PNGs on the fly by Perl Magick.
Essentially, if I turn on Z_FILTERED in the compression code the PNGs will not display, though a casual look over them in a hex editor reveals no problem.
If Z_DEFAULT is used then there is no problem... sorry to be vague about this but I really don't know why this happens and wonder if anyone could give me some clues to what might be up?
Uyen