Editing palette of transparent GIFs

[XnTriq]

• Download and open 28jkub6.gif.
• Go to Image » Edit Palette... and double-click the third color (Index: 2).
• Change the value from R0/G170/B238 to any other color in the color picker and click OK.
• Image colors are all mixed up

[marsh]

Confirmed.

[DOS386]

[*]Image colors are all mixed up

FYI:

[1] The GIF is transparent, 3bpp (!!!), 3 unique colours from 8 (badly optimized), trans index ZERO, colour white ($FF,$FF,$FF)
[2] The GIF has a faulty ratio of 49
[3] Nothing is "mixed up", just the view is "broken", and only if transparency in XN is ON

[XnTriq]

FYI:

[1] The GIF is transparent, 3bpp (!!!), 3 unique colours from 8 (badly optimized), trans index ZERO, colour white ($FF,$FF,$FF)
[2] The GIF has a faulty ratio of 49
[3] Nothing is "mixed up", just the view is "broken", and only if transparency in XN is ON

FYI: Post #97684 is of tangential (!!!) if not ZERO relevance “in this” context

I know perfectly well how to optimize my GIFs.

• 32-bit (16m truecolor + alpha channel) PNG
  vs. 2-bit (4 color palette) GIF

28jkub6.gif is the result of an experiment and was saved with XnView, which doesn't provide export to 2bpp.

The bug is reproducible at any color depth.

[DOS386]

> Image colors are all mixed up

NO. Just the transparent index points to the color edited last time. How to fix? Remember the transparent index before editing the palette and set it back where it used to be.

> The bug is reproducible at any color depth.

Right. I had suspected the GIF to be "strange" ... but it's same for any transparent indexed color images, also PNG.

The problem is always there, but it's visible only if "view transparency" is ON.

PS: GIF ratio 49 is just a silly way to say "1" ... see formula in spec