Compatibility with existing color forumulas

The color formulas for each source are defined in a color file containing the command line arguments to imagemagick convert

We need to translate these to rio color arguments. Two main options

1. Have a rio color --compatability option that will read convert args and interpret them on the fly
2. Script/manually adjust all the color formulas in pxm-sources. Create an alternate color.rio file that mirrors the intent of color but with rio color syntax

Questions:

• what do we do with convert options that don’t translate well to rio color?
• how are we going to visually test to make sure rio color output matches convert’s?

[e-n-f]

Yes, I think LCH is the colorspace that will let you best adjust each of the parameters independent of the others. It should be possible to do it in xyY space too, where hue and saturation are angle and distance on the xy plane independent of lightness on Y, but LCH has the extra convenience of putting gray at the origin instead of at (⅓,⅓) and giving you perceptually uniform hue angles (in exchange for the inconvenience of not being able to mix colors by linear interpolation on the plane).

[celoyd]

The LCH conversion should give better results, and I don’t think the discrepancy is a problem – there’s no color formula that would have been good with IM that will be bad with RC.