It's not a libpng matter but a PNG format matter. The PNG format doesn't store the info you are wanting. As I said, you can make some guesses, but that's not a libpng matter either, but something that could be done in ImageMagick, just as ImageMagick guesses about the JPEG quality. Counting the filter types used is just a matter of examining the PNG file as pngcrush or pngcheck does.fmw42 wrote: ↑2017-08-25T16:32:38-07:00Perhaps you might discuss this with the others on the libpng development team and see if it makes sense to them to modify libpng to show one or the other. I don't know enough about the filter values to say which is better. I would leave that to you and the PNG team to decide which, if they agree to present this information in a new version of libpng.
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