Legacy ImageMagick Discussions Archive

The black channel, K of CMYK, is the amount of (subtractive) black ink, thus 100% is full black. In a grayscale image, colours are additive, so 0 is full black. Oh so this was the idea behind QuantumRange-GetPixelBlack(source_image,p) ! Ok. Why was it failing for grayscale, then? Sorry I edited my ...

So I am happy to report that removing that QuantumRange fixes the issue with negated Black channel. Just recompiled ImageMagick on my Ubuntu machine and the issue is gone. The only thing you need to ensure is that the image that you are "copyingBlack from" does in fact contain Black channel i.e. if ...

In many places around this site, including http://www.imagemagick.org/Usage/bugs/testing/ and here https://www.imagemagick.org/Usage/color_basics/#combine_other the explanation is given as: The last example will not work for 'CMYK' images, as the 'Black' channel image does not actually contain a ...