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I'm having a hard time understanding how palette information is handled in APNG animations that use type PNG_COLOR_TYPE_PALETTE because, apparently, there is little to no documentation.

All PNG_COLOR_TYPE_PALETTE test animation files that I have have just a single PLTE chunk; i.e., all frames share the same global palette. Is this a limitation of the APNG file format; or, can frames also use individual palettes as is possible with GIF, for example? If that is possible, where should the frame-based PLTE chunks go?

Thanks!

greg-tumolo
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Andreas
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2 Answers2

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To validate your answer:

"[The frame data chunk] utilizes the same bit depth, color type, compression method, filter method, interlace method, and palette (if any) as the default image." [https://wiki.mozilla.org/APNG_Specification#.60fdAT.60:_The_Frame_Data_Chunk]

greg-tumolo
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To answer my own question, I've tried several tools which convert GIFs to APNG and when I use them with multi-palette GIFs those tools always remap the frame pixels to one global palette so I guess APNG doesn't support multiple palettes but just a single global palette shared by all frames.

Andreas
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