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imageoptim claim to make smaller pngs than Xcodes does, but I don't understand why Xcode wouldn't just use imageoptim instead if it was better.

Does anyone have some data on imageoptim pngs vrs xcode's PNG compression size and iOS load time?

Glenn Randers-Pehrson
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Robert
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    Xcode's pngcrush is not the real pngcrush (which I wrote). It does some other transformations added by Apple, that cause it to write output that is not a valid PNG (is a CgBI file instead). – Glenn Randers-Pehrson Aug 02 '16 at 15:08
  • @GlennRanders-Pehrson - Oh - I didn't know that! I have updated the question to reflect that (sorry). Do you know if the loading step to convert RGBA to premultiplied BGRA is a trivial step as the `imageoptim` site suggests? Would you suggest using `ImageOptim` for extra compression or leaving xcode's default compression on? – Robert Aug 03 '16 at 10:50
  • Also just saw that `imageoptim` is a suite of tools that includes `pngcrush`. – Robert Aug 03 '16 at 10:51
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    I would simply suggest running your own experiments. Note that if you publish any xcode-optimized PNGs, the aren't really PNGs, and people will come complaining to me about them. Use "pngdefry" to convert them back to real PNGs. – Glenn Randers-Pehrson Aug 03 '16 at 11:15
  • Xcode makes use of a special delivery codec type of PNG internally. It is not the most compressed possible format though, if you want to take a look at an iOS optimized visually lossless delivery codec, have a look at this SO answer. http://stackoverflow.com/a/40255615/763355 – MoDJ Nov 07 '16 at 19:53

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