Is it possible to access original palette for BMP images with bpp<=8?

[zabulus]

To create a homemade algorithm for processing images, we need access to the original palette used during the decoding of BMP files. After examining the source code of BmpDecoderCore, it appears that the palette is only used for color lookups. However, we want to ensure that the original palette is accessible during the processing stage.

[JimBobSquarePants]

We’ve got that already in the main branch for V4 so it wouldn’t be too much to backport

[zabulus]

Could you show me code where I can find this?

[JimBobSquarePants]

Sure. It’s not released yet but the code is here.

https://github.com/SixLabors/ImageSharp/blob/main/src/ImageSharp/Formats/Bmp/BmpMetadata.cs

[zabulus]

yes, looks like what I need.
One more question though. Do you have plans to support indexed pixels as pixel format?

[JimBobSquarePants]

No because indexing is a feature of encoding rather than of a true pixel format. The additional requirement of a lookup table would make many operations impossible. You can see the limitations with libraries like System.Drawing which throws exceptions for many things.