colors.distances: implement CIE76, CIE94, CIEDE2000, and CMC l:c color difference algorithms.

extra/colors/distances/authors.txt

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+John Benediktsson

extra/colors/distances/distances.factor

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+! Copyright (C) 2014 John Benediktsson
+! See http://factorcode.org/license.txt for BSD license
+
+USING: accessors colors colors.lab colors.lch colors.lch.private
+combinators kernel locals math math.functions math.libm
+math.order ;
+
+IN: colors.distances
+
+: rgba-distance ( color1 color2 -- distance )
+    [ >rgba ] bi@
+    [ [ red>> ] bi@ - sq ]
+    [ [ blue>> ] bi@ - sq ]
+    [ [ green>> ] bi@ - sq ] 2tri
+    + + sqrt ;
+
+<PRIVATE
+
+:: mean-hue ( h1 h2 -- mh )
+    h2 h1 - abs 180 > [
+        h1 h2 + dup 360 < [
+            360 + 2 /
+        ] [
+            360 - 2 /
+        ] if
+    ] [
+        h1 h2 + 2 /
+    ] if ;
+
+:: diff-hue ( h1 h2 -- dh )
+    h2 h1 - dup abs 180 > [
+        dup 0 <= [ 360 + ] [ 360 - ] if
+    ] when ;
+
+: sind ( x -- y ) deg>rad sin ;
+
+: cosd ( x -- y ) deg>rad cos ;
+
+: atan2d ( x y -- z ) [ deg>rad ] bi@ fatan2 ;
+
+PRIVATE>
+
+:: CIEDE2000 ( color1 color2 -- distance )
+
+    ! Ensure inputs are L*C*H*
+    color1 >LCHab :> lch1
+    color2 >LCHab :> lch2
+
+    lch1 lch2 [ l>> ] bi@ :> ( l1 l2 )
+    lch1 lch2 [ c>> ] bi@ :> ( c1 c2 )
+    lch1 lch2 [ h>> ] bi@ :> ( h1 h2 )
+
+    ! Calculate the delta values for each channel
+    l2 l1 - :> dl
+    c2 c1 - :> dc
+    c2 c1 * zero? [ 0 ] [ h1 h2 diff-hue ] if
+    2 / sind c1 c2 * sqrt * 2 * :> dh
+
+    ! Calculate mean values
+    l1 l2 + 2 / :> ml
+    c1 c2 + 2 / :> mc
+    c2 c1 * zero? [ 0 ] [ h1 h2 mean-hue ] if :> mh
+
+    ! Lightness weight
+    ml 50 - sq :> mls
+    mls dup 20 + sqrt / 0.015 * 1 + :> sl
+
+    ! Chroma weight
+    mc 0.045 * 1 + :> sc
+
+    ! Hue weight
+    1
+    mh 30 - cosd 0.17 * -
+    mh 2 * cosd 0.24 * +
+    mh 3 * 6 + cosd 0.32 * +
+    mh 4 * 63 - cosd 0.20 * - :> T
+    0.015 mc * T * 1 + :> sh
+
+    ! Rotation term
+    mh 275 - 25 / sq neg e^ 30 * :> dtheta
+    mc 7 ^ dup 25 7 ^ + / sqrt 2 * :> cr
+    dtheta 2 * sind neg cr * :> tr
+
+    ! Final calculation
+    dl sl / sq
+    dc sc /
+    dh sh /
+    [ [ sq ] bi@ ] [ * tr * ] 2bi
+    + + + sqrt ;
+
+:: CIE94 ( color1 color2 -- distance )
+
+    ! Ensure inputs are L*a*b*
+    color1 >laba :> lab1
+    color2 >laba :> lab2
+
+    ! Calculate the delta values for each channel
+    lab1 lab2 [ l>> ] bi@ - :> dl
+    lab1 lab2 [ a>> ] bi@ - :> da
+    lab1 lab2 [ b>> ] bi@ - :> db
+    lab1 [ a>> ] [ b>> ] bi [ sq ] bi@ + sqrt :> c1
+    lab2 [ a>> ] [ b>> ] bi [ sq ] bi@ + sqrt :> c2
+    c1 c2 - :> dc
+    da sq db sq + dc sq - sqrt :> dh
+
+    ! graphics arts:
+    1 0.045 0.015 :> ( kl k1 k2 )
+
+    ! textiles:
+    ! 2 0.048 0.014 :> ( kl k1 k2 )
+
+    kl :> sl
+    k1 c1 * 1 + :> sc
+    k2 c1 * 1 + :> sh
+
+    dl sl / sq
+    dc sc / sq +
+    dh sh / sq + sqrt ;
+
+: CIE76 ( color1 color2 -- distance )
+    [ >laba ] bi@
+    [ [ l>> ] bi@ - sq ]
+    [ [ a>> ] bi@ - sq ]
+    [ [ b>> ] bi@ - sq ] 2tri
+    + + sqrt ;
+
+:: CMC-l:c ( color1 color2 -- distance )
+
+    ! Ensure inputs are L*a*b*
+    color1 >laba :> lab1
+    color2 >laba :> lab2
+
+    lab1 lab2 [ a>> ] bi@ :> ( a1 a2 )
+    lab1 lab2 [ b>> ] bi@ :> ( b1 b2 )
+
+    ! Ensure inputs are L*C*H*
+    color1 >LCHab :> lch1
+    color2 >LCHab :> lch2
+
+    lch1 lch2 [ l>> ] bi@ :> ( l1 l2 )
+    lch1 lch2 [ c>> ] bi@ :> ( c1 c2 )
+    lch1 lch2 [ h>> ] bi@ :> ( h1 h2 )
+
+    a2 a1 - :> da
+    b2 b1 - :> db
+    c2 c1 - :> dc
+    l2 l1 - :> dl
+
+    da sq db sq + dc sq - sqrt :> dh
+
+    l1 16 < [ 0.511 ] [
+        l1 [ 0.040975 * ] [ 0.01765 * 1 + ] bi /
+    ] if :> sl
+
+    c1 [ 0.0638 * ] [ 0.0131 * 1 + ] bi / 0.638 + :> sc
+
+    c1 4 ^ dup 1900 + / sqrt :> F
+
+    h1 164 345 between? [
+        h1 168 + cosd 0.2 * abs 0.56 +
+    ] [
+        h1 35 + cosd 0.4 * abs 0.36 +
+    ] if :> T
+
+    F T * 1 + F - sc * :> sh
+
+    2.0 :> kl ! default lightness
+    1.0 :> kc ! default chroma
+
+    dl kl sl * / sq
+    dc kc sc * / sq
+    dh sh / sq + + sqrt ;

extra/colors/distances/summary.txt

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+Color distance (or Color difference)