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Support of CIE Lab and Lch color spaces is introduced in Quantity_Color: - Enumeration Quantity_TypeOfColor is extended by new values representing CIE Lab and Lch color spaces (with D65 2 deg illuminant). - Conversion of RGB color to and from these color spaces is implemented in Quantity_Color class (within existing API). - Color difference calculation using CIE Delta E 200 formula is implemented in method DeltaE2000(). New methods MakeUniformColors() and SetUniformColors() are added in class AIS_ColorScale, generating and setting color scale based on colors of the same lightness in CIE Lch color model. DRAW commands vcolorconvert and vcolordiff are added to perform conversions and compute difference, respectively. A new option -uniform is added in DRAW command vcolorscale, to set uniform color scale. Added test grid v3d colors (color conversions and difference), test bugs vis bug31454 (uniform color scale)
59 lines
2.3 KiB
Plaintext
59 lines
2.3 KiB
Plaintext
# Check calculation of CIE Ddlta E 2000 color difference
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# Reference data are obtained using online calculator
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# http://brucelindbloom.com/index.html?ColorDifferenceCalc.html
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# or
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# https://cielab.xyz/
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# Second one also shows color and reports if it is out of RGB gamut.
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#
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# Note that values out of RGB gamut would be amended during
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# conversion to RGB and thus the result would be different!
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#
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# Samples aimed at testing discontinuity of CIEDE2000
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# formula are very sensitive to accuracy, we need higher tolerance
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# because conversion is done via RGB floats and loses precision.
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#
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# Format: { {L1 a1 b1} {L2 a2 b2} expected_diff [tolerance] }
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set lab_diff_samples {
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{ # synthetic color pairs }
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{ {0 0 0} {50 0 0} 36.519268 }
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{ {50 0 0} {100 0 0} 36.519268 }
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{ {0 0 0} {100 0 0} 100. }
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{ {20 10 10} {80 10 10} 60. }
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{ {50 0 0} {50 0 50} 23.529412 }
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{ {50 60 60} {50 60 0} 28.016927 }
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{ {30 30 40} {30 30 -60} 44.606253 }
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{ # discontinuity of CIEDE2000 formula }
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{ {30 50.00 40} {20 -10 -8} 39.105394 0.001 }
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{ {30 50.01 40} {20 -10 -8} 43.53247 0.001 }
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{ {20 30.00 30.01} {60 -10 -10} 49.416742 0.05 }
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{ {20 30.01 30.00} {60 -10 -10} 52.448227 0.05 }
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{ # randomly generated data }
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{ {73.4450 34.9839 -24.6753} {87.6216 -18.4863 57.8838} 62.402500 }
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{ {93.6166 -27.3677 29.3893} {46.9191 12.3400 -27.5948} 54.640034 }
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{ {53.9062 61.0929 -51.7583} {65.5157 26.3376 -37.0512} 15.679046 }
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{ {83.6996 9.3358 -24.5571} {93.2268 -3.8589 3.5217} 23.158692 }
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{ {64.8053 -27.3177 -8.9602} {65.8225 37.3192 -38.1465} 34.670514 }
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{ {94.7633 -19.7915 69.2787} {90.9238 -16.7535 4.1936} 26.093024 }
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{ {85.4699 5.6078 -11.1083} {67.9455 -28.4536 7.8808} 31.115070 }
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{ {83.5473 -15.7170 8.3546} {81.3193 -37.2851 57.7090} 19.696753 }
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{ {75.7406 -12.0785 -12.3505} {80.0810 -54.8591 52.1739} 35.834099 }
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{ {62.8209 32.1209 16.9113} {82.1106 25.0843 -7.9416} 21.178519 }
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}
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foreach sample $lab_diff_samples {
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set lab1 [lindex $sample 0]
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if { $lab1 == "#" } continue
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set lab2 [lindex $sample 1]
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set dref [lindex $sample 2]
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set diff [vcolordiff {*}[vcolorconvert from lab {*}$lab1] {*}[vcolorconvert from lab {*}$lab2]]
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# use tolerance 1e-4 except if other value is defined in sample data
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set tol [lindex $sample 3]
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if { $tol == "" } { set tol 1e-4 }
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checkreal "CIEDE2000 diff of Lab colors ($lab1) and ($lab2)" $diff $dref $tol 1e-6
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}
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