I process scanned pages of text. Some of these pages show blue pen notes, which I want to replace with another colour.
Every pixel within a blue pen note shows a higher value in the Blue channel, compared to Red and Green channels. I'd like to use this ratio as a pixel selector, as this is the common denominator with respect to the whole page.
I already tried alternatives like below, but at some point, parts of the black text become filled with red.
I figure I need to separate the channels and then compare the values via fx, but I am not sure how to do that.
Code: Select all
convert image.jpg -fuzz 45% -fill red -opaque 'srgb(0,0,255)' 0672.jpg
https://drive.google.com/file/d/0BxivpP ... sp=sharing