Yes, I see that wd do what I want, *but* my image has several different, unconnected areas of black (i.e. letters) which I want to turn into blue, and as I read ColorFloodfill, I wd have to specify a pixel in each of these, which wd be laborious. Is it the right kind of laziness to want a method that will turn all black pixels blue??
PS - what is the "color" parameter for in method Colorize? - the same thing happens whatever I set this to!
From what I can see you have to define the exact coordinates of the pixel that needs rendering. The same goes for Image::XPM and others.
I hate to say this, but, do you have to use Perl for this solution? A lot of graphic packages have batch conversion tools these days. You could make changes to the colour pallete and batch convert a number of images from there.