How do I use a colour to mask out pixels?
Actually that's how I'm trying to solve my problem. My real problem, and perhaps there's a more direct solution, is that I want yellow pixels to be white and anything that isn't yellow to be black. But I realize yellow is Red + Green (two channels). So the idea of using blue as a mask is how I think I might achieve that, but perhaps that's the wrong way. If there is a more direct way to isolate the yellow that would be better. By yellow I define that to mean the Red channel >90% and the Green channel is also >90%.
Thanks in advance.
$ convert -version
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