# Check calculation of CIE Ddlta E 2000 color difference # Reference data taken from # "The CIEDE2000 Color-Difference Formula: Implementation Notes, # Supplementary Test Data, and Mathematical Observations", # G. Sharma, W. Wu, E. N. Dalal, # Color Research and Application, vol. 30. No. 1, pp. 21-30, February 2005 # http://www2.ece.rochester.edu/~gsharma/ciede2000/ # # Note: samples 1 to 6 and 28 are commented because the colors # are out of RGB gamut. # Samples 10 and 15 are aimed at testing discontinuity of CIEDE2000 # formula and so are very sensitive to accuracy, we need higher tolerance # because conversion is done via RGB floats and loses precision. # # Format: L1 a1 b1 L2 a2 b2 expected_diff [tolerance] set lab_diff_samples { # 50.0000 2.6772 -79.7751 50.0000 0.0000 -82.7485 2.0425 # 50.0000 3.1571 -77.2803 50.0000 0.0000 -82.7485 2.8615 # 50.0000 2.8361 -74.0200 50.0000 0.0000 -82.7485 3.4412 # 50.0000 -1.3802 -84.2814 50.0000 0.0000 -82.7485 1.0000 # 50.0000 -1.1848 -84.8006 50.0000 0.0000 -82.7485 1.0000 # 50.0000 -0.9009 -85.5211 50.0000 0.0000 -82.7485 1.0000 50.0000 0.0000 0.0000 50.0000 -1.0000 2.0000 2.3669 50.0000 -1.0000 2.0000 50.0000 0.0000 0.0000 2.3669 50.0000 2.4900 -0.0010 50.0000 -2.4900 0.0009 7.1792 50.0000 2.4900 -0.0010 50.0000 -2.4900 0.0010 7.1792 0.05 50.0000 2.4900 -0.0010 50.0000 -2.4900 0.0011 7.2195 50.0000 2.4900 -0.0010 50.0000 -2.4900 0.0012 7.2195 50.0000 -0.0010 2.4900 50.0000 0.0009 -2.4900 4.8045 50.0000 -0.0010 2.4900 50.0000 0.0010 -2.4900 4.8045 50.0000 -0.0010 2.4900 50.0000 0.0011 -2.4900 4.7461 0.06 50.0000 2.5000 0.0000 50.0000 0.0000 -2.5000 4.3065 50.0000 2.5000 0.0000 73.0000 25.0000 -18.0000 27.1492 50.0000 2.5000 0.0000 61.0000 -5.0000 29.0000 22.8977 50.0000 2.5000 0.0000 56.0000 -27.0000 -3.0000 31.9030 50.0000 2.5000 0.0000 58.0000 24.0000 15.0000 19.4535 50.0000 2.5000 0.0000 50.0000 3.1736 0.5854 1.0000 50.0000 2.5000 0.0000 50.0000 3.2972 0.0000 1.0000 50.0000 2.5000 0.0000 50.0000 1.8634 0.5757 1.0000 50.0000 2.5000 0.0000 50.0000 3.2592 0.3350 1.0000 60.2574 -34.0099 36.2677 60.4626 -34.1751 39.4387 1.2644 63.0109 -31.0961 -5.8663 62.8187 -29.7946 -4.0864 1.2630 61.2901 3.7196 -5.3901 61.4292 2.2480 -4.9620 1.8731 # 35.0831 -44.1164 3.7933 35.0232 -40.0716 1.5901 1.8645 22.7233 20.0904 -46.6940 23.0331 14.9730 -42.5619 2.0373 36.4612 47.8580 18.3852 36.2715 50.5065 21.2231 1.4146 90.8027 -2.0831 1.4410 91.1528 -1.6435 0.0447 1.4441 90.9257 -0.5406 -0.9208 88.6381 -0.8985 -0.7239 1.5381 6.7747 -0.2908 -2.4247 5.8714 -0.0985 -2.2286 0.6377 2.0776 0.0795 -1.1350 0.9033 -0.0636 -0.5514 0.9082 } set index -1 foreach sample [split $lab_diff_samples \n] { incr index set lab1 [lrange $sample 0 2] if { [lindex $lab1 0] == "#" || $lab1 == "" } continue set lab2 [lrange $sample 3 5] set dref [lindex $sample 6] set diff [vcolordiff {*}[vcolorconvert from lab {*}$lab1] {*}[vcolorconvert from lab {*}$lab2]] # use tolerance 1e-3 except if other value is defined in sample data set tol [lindex $sample 7] if { $tol == "" } { set tol 1e-3 } checkreal "Sample $index: Lab ($lab1) and ($lab2), diff" $diff $dref $tol 1e-6 }