Ben Goren wrote:
Given a particular image, is there a relatively painless way to calculate the optimal color space for editing?
tiffgamut, iccgamut and viewgamut -i are the argyll tools you need. viewgamut -i calculates gamut- and intersecton-volumes.
When you have to use this tools frequently, it might be convenient to write a little shell script that compares the gamut of a given image with your favorite editing spaces.