coltgt: colour target printing a few patches for display colour management
this module outputs the ColorChecker24 patches in bt2020, plus an additional row with fully saturated bt2020 primaries as well as the mixed coordinates for magenta, yellow, and cyan.
this can be useful in conjunction with say argyll's spotread to verify a display colour management setup.
the bottom two rows contain a stripe pattern with 50% grey and 50% black pixels, as well as a row with the linear averages. if your monitor gamma is set correctly and the colour profile is correct, these two should look the same if viewed at 100% zoom from some distance. sometimes it's necessary to move the window around a bit to avoid resampling issues. also make sure you don't use fractional scaling in your compositor, leave the content scale factor at integer values.
