# Check conversion of RGB colors to CIE Lab color space

# Samples are obtained (with Ref. White D65, Gamma = 1 for linear RGB) using
# http://brucelindbloom.com/index.html?ColorCalculator.html
set rgb_to_lab_samples {
  { # black, white, 50% gray }
  { {0 0 0} {0 0 0} }
  { {1 1 1} {100 0 0} }
  { {0.5 0.5 0.5} {76.0693 0 0} }

  { # pure colors }
  { {1 0 0} {53.2408 80.0925 67.2032} }
  { {0 1 0} {87.7347 -86.1827 83.1793} }
  { {0 0 1} {32.2970 79.1875 -107.8602} }
  { {0 1 1} {91.1132 -48.0875 -14.1312} }
  { {1 1 0} {97.1393 -21.5537 94.4780} }
  { {1 0 1} {60.3242 98.2343 -60.8249} }

  { # shades of pure red }
  { {0.1 0 0} {16.1387 37.1756 25.0600} }
  { {0.3 0 0} {30.3521 53.6166 44.0349} }
  { {0.5 0 0} {38.9565 63.5695 53.3392} }
  { {0.7 0 0} {45.4792 71.1144 59.6700} }
  { {0.9 0 0} {50.8512 77.3285 64.8840} }

  { # random colors }
  { {0.3 0.5 0.9} {75.2228 0.7560 -31.8425} }
}

foreach sample $rgb_to_lab_samples {
  set rgb [lindex $sample 0]
  if { $rgb == "#" } continue

  set ref [lindex $sample 1]
  set lab [vcolorconvert to lab {*}$rgb]
  check3reals "RGB ($rgb) to Lab" {*}$lab {*}$ref 1e-4
}