Rec. 601 luma from 8-bit RGB, rounded to an integer.
Rounded deliberately: the result crosses the CDP boundary as JSON, where an
integer costs ~4 characters and an unrounded double costs ~20. The lost
precision is under half a grey level, which is four orders of magnitude below
the ~0.45 correlation gap this feeds — see COMPARE_SIZE.
Rec. 601 luma from 8-bit RGB, rounded to an integer.
Rounded deliberately: the result crosses the CDP boundary as JSON, where an integer costs ~4 characters and an unrounded double costs ~20. The lost precision is under half a grey level, which is four orders of magnitude below the ~0.45 correlation gap this feeds — see
COMPARE_SIZE.