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Paletted image with alpha channel

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Sounds like PNG-8


try looking through the filetype index - I haven't seen it but I haven't had a use for it.




The built-in PNG filetype has been able to save 8-bit images since Paint.NET 3.30.

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paint.net default png exporter only can export 8bit images with 1 bit alpha which is not what I need.

Verified. I wonder if this is a bug or a limitation of the output format.


Zoom in and check the edges of this circle. The alpha was converted to the secondary color during the save process.

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there was a plugin that allows to save aplha in 32bit BMP, that would be enough to me to add low color support there even though its kind of hack as well. I also thought about targas, not sure if specs allow to save alpha in palette, yet the space is there. would like to stick to easy uncompressed format as I had both bmp and tga reading implemented.

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Sorry to say but PNG does not allow to combine a paletted image with an 8-bit apha channel.

There is RGB-A and Gray-A but no Palette-A.

A palette entry may have a exactly one alpha value. To use an RGB value with different alpha you have to put it multiple times into the palette. But this reduces the amount of possible colors.


But maybe I'm wrong? ;-)


I implemented this ones in PDNAnimator which converts PDN files to APNG animations. The code contains an optimzation step which tries to create a paletted apng with transparency. But this makes only some sense if you are using not more than 32 colors.

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  • 2 weeks later...

Sorry to say but PNG does not allow to combine a paletted image with an 8-bit apha channel.


I'm interested to find a format that may support this way to store a picture, not PNG in particular. if you'll check BMP, it is possible to use 32 bit color in palette, except BMP doesn't use transparency at all. but technically it fits well to save the image by the analogy with alpha BMP plugin.

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