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MyPaint opens but won't save 16-bit files #4

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achadwick opened this Issue Jun 23, 2014 · 2 comments

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achadwick commented Jun 23, 2014

Migrated from Gna! bug 21650:

MyPaint can load 16 bit per channel OpenRaster files, but can only save 8 bit per channel OpenRaster; inspecting files saved by MyPaint reveals 8-bit PNG inside.
Saving 16-bit files is required for 16-bit workflow across several applications, e.g. with addition of Krita or GIMP 2.10
-- Sergey Davidoff (shnatsel)

@achadwick achadwick added this to the Post-1.2 milestone Jun 23, 2014

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achadwick commented Jun 23, 2014

Trying to remember why we're holding off on this originally. I think it's because I wanted to investigate using 16 bit saves to flag linear-light compositing - but never got round to it, obviously.

There are probably better, magic-free, ways of doing that, but it's probably something that should be explicitly noted in OpenRaster.

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martinxyz commented Jun 24, 2014

How could this be addressed?

  • Always save 16bpc. (I think libpng does auto-conversion for applications that don't support it. But: file size. It's already huge for simple one-layer images because of mergedimage.png. And now including lossless compression of all MyPaint quantization artifacts?)
  • Ask the user. ("Huh, ORA? And what is a bpc? I only wanted to save.")
  • Silently preserve 16bpc. (Per-layer memory; but how can the user control it? Global preference "always save everything 16bpc", off by default?)

From the options above I think I would prefer the first one. But adding linear light and color management might change our options.

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