Legacy ImageMagick Discussions Archive

Great! Thank you.

Hmm.. Both fail to preserve the colors behind the blue section and turn them to complete grayscale. Pure blue (#0000FF) should be completely grayscale, but colors such as purple or cyan should lose their saturation only partially, proportionally to their "blue-ness". I hope this makes sense. :D http ...

You're right: what I really want is to replace shades of blue with shades of gray.
Can the mask be non-monotone? I'd like to preserve the shades brightness, so alpha is a must.

From this, to That:

Related to my question question about negating only non-saturated colors , I would like to know how to convert a specific [s]channel[/s] color (say blue) to grayscale. I tried to do it with a mask, but the b I used instead of g in the -channel option doesn't seem to refer to the b lue channel ...

Brilliant. Thank you! For future reference: convert neg-bw1.png -colorspace HSB -channel g -separate +channel -threshold 0% mask convert neg-bw1.png \( -clone 0 -negate \) \( -clone 0 -colorspace HSB -channel g -separate +channel -threshold 0% -negate \) -compose over -composite neg-bw1.png_lowsat ...

Your suggestion produces this; and by stripping out blur, I get:


It's not bad, but we're not quite there yet either. How come the negative of white didn't come out black?

Can ImageMagick negate only non-saturated colors (black, white, and gray)?

I tried negating the whole image before rotating the hue, but that didn't produce the expected result.

My image, and the expected result: