Legacy ImageMagick Discussions Archive

convert image -colorspace LAB \
-channel G -evaluate multiply $afactor +channel \
-channel B -evaluate multiply $bfactor +channel \
-colorspace sRGB resultimage

You can also try

convert image -colorspace HCL \
-channel G -evaluate multiply 0.8 +channel \
-colorspace sRGB resultimage

The first ...

Thanks a lot for your replies! I'll check it at Monday.

I believe that modulate has been modified recently (IM 6.7.9.0) to allow it to work in HCL colorspace using -define modulate:colorspace=HCL
see http://www.imagemagick.org/Usage/color_mods/#modulate_colorspace
If this does not work, then get back and I will help decompose HCL colorspace to modify ...

I want to change chroma (in the sense of the LCHab color space) of an image with some command-line utility. I think ImageMagick is suitable for this task.

I see the modulate command, but it operates only with HSB, HSL and HWB color spaces and affects saturation, not chroma.

It can be done manually ...