Some color information is lost when loading images saved as 24-bit bmp


This doesn’t happen very often, but I thought it was worth reporting.

It should simply never happen, BMP is a plain and non-lossy bitmap image format, where data is saved as a raw sequence (array) of bytes. It should be a pretty standard format.

Which application was the original image created and saved with?
Or is this a problem happening entirely within PM NG?

Was the image created (drawn) in PM or was it imported from another application or format?

The whole process was conducted with PM NG.
I know that there is no loss of data in bmp.
So I thought it was a bug and reported it

I think this should be fixed with upcoming V8 beta 4.

When transforming 24Bit images to indexed 8 bit then color quantization mechanisms are used. They try to find best colors to be used out of the (theoretically Mio) different ones. These transformations tend to omit colors by using one for a bunch of similar colors. The mechanisms have no check if the overall number of colors that are effectively used are already less then 256.
In that case they can be used 1:1 and there would be no need to do special transformations based on the whole maximum 24Bit color space.

Now PM checks if the colors are less/equal to 256 and if so it just collects and uses them.

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Thank you for GREAT WORK!