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Added on 2/7/2006
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I have added my colour conversion handlers for anyone interested. I have not tested them all, but they are straight conversions from the information gleaned from the links which I've also provided. If you are interested in further information and other conversions or the introduction to a complicated world of accurate colour reproduction/reprsentation then the links will also be helpful in that regard. Enjoy!
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-- http://www.easyrgb.com/math.html
-- http://www.brucelindbloom.com/index.html?Equations.html -- http://www.cs.rit.edu/~ncs/color/a_spaces.html -- http://www.f4.fhtw-berlin.de/~barthel/ImageJ/ColorInspector/HTMLHelp/farbraumJava.htm -- http://www.efg2.com/Lab/Graphics/Colors/index.html -- http://www.nebulus.org/tutorials/2d/photoshop/color/index.html on CMYKtoRGB (C, M, Y, K) if C > 1 or M > 1 or Y > 1 or K > 1 then C = C / 100.0 M = M / 100.0 Y = Y / 100.0 K = K / 100.0 end if R = (1 - C * (1 - K) - K) * 256 G = (1 - M * (1 - K) - K) * 256 B = (1 - Y * (1 - K) - K) * 256 return color(R, G, B) end on RGBtoCMYK (R, G, B) C = 1 - (R / 255.0) M = 1 - (G / 255.0) Y = 1 - (B / 255.0) if min(C, M, Y) = 1 then return [0, 0, 0, 1] K = min(C,M,Y) C = (C - K) / (1 - K) M = (M - K) / (1 - K) Y = (Y - K) / (1 - K) the floatPrecision = 3 return [C, M, Y, K] end on RGBtoCMY (R, G, B) C = 1 - (R / 255.0) M = 1 - (G / 255.0) Y = 1 - (B / 255.0) return [C, M, Y] end on CMYtoRGB (C, M, Y) if C > 1 or M > 1 or Y > 1 then C = C / 100.0 M = M / 100.0 Y = Y / 100.0 K = K / 100.0 end if R = (1 - C) * 255 G = (1 - M) * 255 B = (1 - Y) * 255 return color(R, G, B) end on CMYtoCMYK (C, M, Y) K = 1 if C < K then K = C if M < K then K = M if Y < K then K = Y C = (C - K) / (1 - K) M = (M - K) / (1 - K) Y = (Y - K) / (1 - K) return [C, M, Y, K] end on CMYKtoCMY (C, M, Y, K) C = ( C * ( 1 - K ) + K ) M = ( M * ( 1 - K ) + K ) Y = ( Y * ( 1 - K ) + K ) return [C, M, Y] end on RGBtoHex(R, G, B) return color(R, G, B).hexString() end on HextoRGB(aHex) return rgb(aHex) end -- 0, 3, 6, 9, C, F -- 0%, 20%, 40%, 60%, 80%, 100% on RGBtoWebSafe(R, G, B) webSafe = [0, 51, 102, 153, 204, 255] webSafe.sort() R1 = webSafe[webSafe.findPosNear(R)] if R < max(0, R1 - 25.5) then R1 = webSafe[max(1,webSafe.getPos(R) - 1)] G1 = webSafe[webSafe.findPosNear(G)] if G < max(0, G1 - 25.5) then G1 = webSafe[max(1,webSafe.getPos(G) - 1)] B1 = webSafe[webSafe.findPosNear(B)] if B < max(0, B1 - 25.5) then B1 = webSafe[max(1,webSafe.getPos(B) - 1)] aColor = rgb(R1, G1, B1) return aColor.hexString() end on WebSafetoRGB(aHex) webSafe = ["0": 0, "3": 51, "6": 102, "9": 153, "C": 204, "F": 255] R = webSafe.getProp(aHex.char[2]) G = webSafe.getProp(aHex.char[4]) B = webSafe.getProp(aHex.char[6]) return color(R, G, B) end on HextoWebSafe(aHex) aColor = rgb(aHex) webSafe = [0, 51, 102, 153, 204, 255] webSafe.sort() R = webSafe[webSafe.findPosNear(aColor.red)] if aColor.red < max(0, R - 25.5) then R = webSafe[max(1,webSafe.getPos(R) - 1)] G = webSafe[webSafe.findPosNear(aColor.green)] if aColor.green < max(0, G - 25.5) then G = webSafe[max(1,webSafe.getPos(G) - 1)] B = webSafe[webSafe.findPosNear(aColor.blue)] if aColor.blue < max(0, B - 25.5) then B = webSafe[max(1,webSafe.getPos(B) - 1)] aColor = rgb(R, G, B) return aColor.hexString() end -- Colour Conversion Algorithms -- http://www.easyrgb.com/math.html -- http://www.cs.rit.edu/~ncs/color/t_convert.html -- RGB to Hue, Saturation, Value on RGBtoHSV(R, G, B) R = R / 255.0 G = G / 255.0 B = B / 255.0 aMin = min(R, G, B) aMax = max(R, G, B) delta = aMax - aMin V = aMax if aMax = 0 then S = 0 H = 0 else S = delta / float(aMax) if R = aMax then H = (G - B) / float(delta) else if G = aMax then H = 2 + (B - R) / float(delta) else H = 4 + (R - G) / float(delta) end if H = 60 * H if H < 0 then H = H + 360 end if return [H, S, V] end on RGBtoHSB (R, G, B) return RGBtoHSV(R, G, B) end on HSVtoRGB(H, S, V) if S = 0 then R = V G = V B = V end if H = H / 60.0 i = integer(H - 0.499999) f = H - i p = V * (1 - S) q = V * (1 - S * f) t = V * (1 - S * (1 - f)) Case i of 0: R = V G = t B = p 1: R = p G = v B = p 2: R = p G = V B = t 3: R = p G = q B = V 4: R = t G = p B = V otherwise R = V G = p B = q end Case return color(R * 255, G * 255, B * 255) end on HSBtoRGB (H, S, B) return HSVtoRGB(H, S, B) end -- RGB to Hue, Saturation, Lightness on RGBtoHSL (R, G, B) R = R / 255.0 G = G / 255.0 B = B / 255.0 aMin = min(R, G, B) aMax = max(R, G, B) delta = aMax - aMin L = (aMax + aMin ) / 2 if aMax = 0 then S = 0 H = 0 else if L < 0.5 then S = delta / ( aMax + aMin ) else S = delta / ( 2 - aMax - aMin ) end if if R = aMax then H = (G - B) / float(delta) else if G = aMax then H = 2 + (B - R) / float(delta) else H = 4 + (R - G) / float(delta) end if H = 60 * H if H < 0 then H = H + 360 end if return [H, S, L] end -- this function calls another function: HuetoRGB( v1, v2, vH ) on HSLtoRGB (H, S, L) if S = 0 then -- HSL values 0-360, 0-1, 0-1 R = L * 255 --RGB results = 0 - 255 G = L * 255 B = L * 255 else if L < 0.5 then temp2 = L * (1.0 + S) else temp2 = (L + S) - (S * L) end if if H > 1 then H = H / 360.0 -- HSL values = 0 - 1 temp1 = (2.0 * L) - temp2 R = 255 * HuetoRGB( temp1, temp2, H + ( 1.0 / 3.0 ) ) G = 255 * HuetoRGB( temp1, temp2, H ) B = 255 * HuetoRGB( temp1, temp2, H - ( 1.0 / 3.0 ) ) end if return color(R, G, B) end on HuetoRGB( v1, v2, vH ) if vH < 0 then vH = vH + 1 if vH > 1 then vH = vH - 1 if ( 6 * vH ) < 1 then put (v1 + ( v2 - v1 ) * 6 * vH) return (v1 + ( v2 - v1 ) * 6 * vH) end if if ( 2 * vH ) < 1 then put v2 return v2 end if if ( 3 * vH ) < 2 then put (v1 + ( v2 - v1 ) * ( ( 2.0 / 3.0 ) - vH ) * 6) return (v1 + ( v2 - v1 ) * ( ( 2.0 / 3.0 ) - vH ) * 6) end if return v1 end on RGBtoXYZ (R, G, B) R = ( R / 255.0 ) --Where R = 0 - 255 G = ( G / 255.0 ) --Where G = 0 - 255 B = ( B / 255.0 ) --Where B = 0 - 255 if R > 0.04045 then R = power((( R + 0.055 ) / 1.055 ), 2.4) else R = R / 12.92 end if if G > 0.04045 then G = power((( G + 0.055 ) / 1.055 ), 2.4) else G = G / 12.92 end if if B > 0.04045 then B = power((( B + 0.055 ) / 1.055 ), 2.4) else B = B / 12.92 end if R = R * 100 G = G * 100 B = B * 100 --Observer. = 2°, Illuminant = D65 X = (0.412453 * R) + (0.357580 * G) + (0.180423 * B) Y = (0.212671 * R) + (0.715160 * G) + (0.072169 * B) Z = (0.019334 * R) + (0.119193 * G) + (0.950227 * B) return [X, Y, Z] end on XYZtoRGB (X, Y, Z) X = X / 100.0 --Where X = 0 - 95.047 Y = Y / 100.0 --Where Y = 0 - 100.000 Z = Z / 100.0 --Where Z = 0 - 108.883 --Observer = 2°, Illuminant = D65 R = (3.240479 * X) + (-1.537150 * Y) + (-0.498535 * Z) G = (-0.969256 * X) + (1.875992 * Y) + (0.041556 * Z) B = (0.055648 * X) + (-0.204043 * Y) + (1.057311 * Z) if ( R > 0.0031308 ) then R = 1.055 * power(R, 1 / 2.4) - 0.055 else R = 12.92 * R end if if ( G > 0.0031308 ) then G = 1.055 * power(G, 1 / 2.4) - 0.055 else G = 12.92 * G end if if ( B > 0.0031308 ) then B = 1.055 * power(B, 1 / 2.4) - 0.055 else B = 12.92 * B end if R = R * 255 G = G * 255 B = B * 255 return color(R, G, B) end on XYZtoCIELab (X, Y, Z) -- Observer= 2°, Illuminant= D65 X = X / 95.047 --refX = 95.047 Y = Y / 100.000 --refY = 100.000 Z = Z / 108.883 --refZ = 108.883 if ( X > 0.008856 ) then X = power(X, 1.0/3.0) else X = ( 7.787 * X ) + ( 16.0 / 116.0 ) end if if ( Y > 0.008856 ) then Y = power(Y, 1.0/3.0) else Y = ( 7.787 * Y ) + ( 16.0 / 116.0 ) end if if ( Z > 0.008856 ) then Z = power(Z, 1.0/3.0) else Z = ( 7.787 * Z ) + ( 16.0 / 116.0 ) end if L = ( 116 * Y ) - 16 a = 500 * ( X - Y ) b = 200 * ( Y - Z ) return [L, a, b] end on CIELabtoXYZ (L, a, b) Y = ( L + 16 ) / 116.0 X = ( a / 500.0 )+ Y Z = Y - ( b / 200.0 ) if ( power(Y, 3) > 0.008856 ) then Y = power( Y, 3) else Y = ( Y - (16.0 / 116.0 )) / 7.787 end if if ( power(X, 3) > 0.008856 ) then X = power(X, 3) else X = ( X - (16.0 / 116.0) ) / 7.787 end if if ( power(Z, 3) > 0.008856 ) then Z = power(Z, 3) else Z = ( Z - (16.0 / 116.0) ) / 7.787 end if X = 95.047 * X --refX = 95.047 Observer= 2°, Illuminant= D65 Y = 100.000 * Y --refY = 100.000 Z = 108.883 * Z --refZ = 108.883 return [X, Y, Z] end on XYZtoCIELuv (X, Y, Z) U = ( 4 * X ) / ( X + ( 15 * Y ) + ( 3 * Z ) ) V = ( 9 * Y ) / ( X + ( 15 * Y ) + ( 3 * Z ) ) Y = Y / 100.0 if ( Y > 0.008856 ) then Y = power(Y, 1/3.0) else Y = ( 7.787 * Y ) + ( 16 / 116.0 ) end if refX = 95.047 --Observer= 2°, Illuminant= D65 refY = 100.000 refZ = 108.883 refU = ( 4 * refX ) / ( refX + ( 15 * refY ) + ( 3 * refZ ) ) refV = ( 9 * refY ) / ( refX + ( 15 * refY ) + ( 3 * refZ ) ) L = ( 116 * Y ) - 16 U = 13 * L * ( U - refU ) V = 13 * L * ( V - refV ) return [L, U, V] end on CIELuvtoXYZ (L, U, V) Y = ( L + 16 ) / 116.0 if ( power(Y, 3) > 0.008856 ) then Y = power(Y, 3) else Y = ( Y - (16 / 116.0) ) / 7.787 end if refX = 95.047 --Observer= 2°, Illuminant= D65 refY = 100.000 refZ = 108.883 refU = ( 4 * refX ) / ( refX + ( 15 * refY ) + ( 3 * refZ ) ) refV = ( 9 * refY ) / ( refX + ( 15 * refY ) + ( 3 * refZ ) ) U = U / ( 13 * L ) + refU V = U / ( 13 * L ) + refV Y = Y * 100 X = - ( 9 * Y * U ) / ( ( U - 4 ) * V - U * V ) Z = ( 9 * Y - ( 15 * V * Y ) - ( V * X ) ) / ( 3 * V ) return [X, Y, Z] end on XYZtoHunterLab (X, Y, Z) HL = 10 * sqrt( Y ) Ha = 17.5 * ( ( ( 1.02 * X ) - Y ) / sqrt( Y ) ) Hb = 7 * ( ( Y - ( 0.847 * Z ) ) / sqrt( Y ) ) return [HL, Ha, Hb] end on HunterLabtoXYZ (HL, Ha, Hb) Y = HL / 10 X = Ha / 17.5 * HL / 10 Z = Hb / 7 * HL / 10 Y = power(Y,2) X = ( X + Y ) / 1.02 Z = -( Z - Y ) / 0.847 return [X, Y, Z] end --Where X = 0 - 95.047 Observer. = 2°, Illuminant = D65 --Where Y = 0 - 100.000 --Where Z = 0 - 108.883 on XYZtoYxy (X, Y, Z) Y = Y xx = X / ( X + Y + Z ) yy = Y / ( X + Y + Z ) return [Y, xx, yy] end --Where Y = 0 - 100 --Where xx = 0 - 1 --Where yy = 0 - 1 on YxytoXYZ (Y, xx, yy) X = xx * ( Y / yy ) Y = Y Z = ( 1 - xx - yy ) * ( Y / yy ) return [X, Y, Z] end -- The YIQ system is the colour primary system -- adopted by NTSC for colour television broadcasting on RGBtoYIQ (R, G, B) Y = (0.299 * R) + (0.587 * G) + (0.114 * B) I = (0.596 * R) + (-0.275 * G) + (-0.321 * B) Q = (0.212 * R) + (-0.523 * G) + (0.311 * B) return [Y, I, Q] end on YIQtoRGB (Y, I, Q) R = (1.0 * Y) + (0.956 * I) + (0.621 * Q) G = (1.0 * Y) + (-0.272 * I) + (-0.647 * Q) B = (1.0 * Y) + (-1.105 * I) + (1.702 * Q) return color(R, G, B) end -- YUV is like YIQ, except that it is the PAL/European standard on RGBtoYUV (R, G, B) Y = (0.299 * R) + (0.587 * G) + (0.114 * B) U = (-0.147 * R) + (-0.289 * G) + (0.437 * B) V = (0.615 * R) + (-0.515 * G) + (-0.100 * B) return [Y, U, V] end on YUVtoRGB (Y, U, V) R = (1.0 * Y) + (0.0 * U) + (1.140 * V) G = (1.0 * Y) + (-0.394 * U) + (-0.581 * V) B = (1.0 * Y) + (2.028 * U) + (0.0 * V) return color(R, G, B) end -- ****************************************************************** -- Sub Functions -- ****************************************************************** on CIELabtoRGB (L, a, b) XYZ = CIELabToXYZ(L, a, b) return XYZtoRGB(XYZ[1], XYZ[2], XYZ[3]) end on RGBtoCIELab (R, G, B) XYZ = RGBtoXYZ(R, G, B) return XYZtoCIELab (XYZ[1], XYZ[2], XYZ[3]) end -- ********************************************************************************* -- XYZ (Tristimulus) Reference values of a perfect reflecting diffuser -- ********************************************************************************* -- Observer 2° (CIE 1931) 10° (CIE 1964) --Illuminant X2 Y2 Z2 X10 Y10 Z10 -- --A (Tungsten) 109.850 100.0 35.585 111.144 100.0 35.200 --C 98.074 100.0 118.232 97.285 100.0 116.145 --D50 96.422 100.0 82.521 96.720 100.0 81.427 --D55 95.682 100.0 92.149 95.799 100.0 90.926 --D65 (Daylight) 95.047 100.0 108.883 94.811 100.0 107.304 --D75 94.972 100.0 122.638 94.416 100.0 120.641 --D93 (CRT monitor) --F2 (Fluorescent) 99.187 100.0 67.395 103.280 100.0 69.026 --F7 95.044 100.0 108.755 95.792 100.0 107.687 --F11 100.966 100.0 64.370 103.866 100.0 65.620 --Temperature x y Dir y/x --(Kelvin) --2000 0.52669 0.41331 1.33101 --2105 0.51541 0.41465 1.39021 --2222 0.50338 0.41525 1.45962 --2353 0.49059 0.41498 1.54240 --2500 0.47701 0.41368 1.64291 --2677 0.463 0.41121 1.76811 % error in table [3], estimated values --2857 0.446 0.40742 1.92863 --3077 0.43156 0.40216 2.14300 --3333 0.41502 0.39535 2.44455 --3636 0.39792 0.38690 2.90309 --4000 0.38045 0.37676 3.68730 --4444 0.36276 0.36496 5.34398 --5000 0.34510 0.35162 11.17883 --5714 0.32775 0.33690 -39.34888 --6667 0.31101 0.32116 -6.18336 --8000 0.29518 0.30477 -3.08425 --10000 0.28063 0.28828 -1.93507 -- ************************************************************ -- The below are from: -- http://www.srgb.com/hpsrgbprof/sld001.htm -- however, I do not know if the math is correct -- ************************************************************ on XYZD65toXYZD50 (X65, Y65, Z65) X50 = (1.0479 * X65) + (.0229 * Y65) + (-0.0502 * Z65) Y50 = (.0296 * X65) + (.9904 * Y65) + (-0.0171 * Z65) Z50 = (-0.0092 * X65) + (.0151 * Y65) + (.7519 * Z65) return [X50, Y50, Z50] end -- 2.2 Gamma on XYZD50toRGB (X, Y, Z) R = (.4361 * X) + (.2664 * Y) + (.1431 * Z) G = (.2225 * X) + (.7169 * Y) + (.0606 * Z) B = (.0139 * X) + (.0971 * Y) + (.7141 * Z) return color(R, G, B) end --on XYZtoRGB (X, Y, Z) -- R = (.8951 * X) + (.2664 * Y) + (-0.1614 * Z) -- G = (-0.7502 * X) + (1.7135 * Y) + (.0367 * Z) -- B = (.0389 * X) + (.0685 * Y) + (1.0296 * Z) -- return color(R, G, B) --end -- Gamma Equation -- For each R, G, B value: -- if RGB <= 0.03928 -- RGB' = RGB/12.92 -- else -- RGB' = power((0.55 + RGB)/1.055), 2.4) -- end if -- Note: RGB normalized to 0.0 to 0.1 --on ceil myNum -- --return integer(myNum + 0.499999999999999) -- --end -- --on floor myNum -- --return integer(myNum - 0.499999999999999) -- --end --ITU-R BT.709 Primaries and white point D65 [9]. Valid for sRGB. on sRGBtoXYZ (R, G, B) R = R/255.0 G = G/255.0 B = B/255.0 X = (0.4124 * R) + (0.3576 * G) + (0.1805 * B) Y = (0.2126 * R) + (0.7152 * G) + (0.0722 * B) Z = (0.0193 * R) + (0.1192 * G) + (0.9505 * B) return [X * 100, Y * 100, Z * 100] end on XYZtosRGB (X, Y, Z) X = X/100.0 Y = Y/100.0 Z = Z/100.0 R = (3.2410 * X) + (-1.5374 * Y) + ( -0.4986 * Z) G = (-0.9692 * X) + ( 1.8760 * Y) + ( 0.0416 * Z) B = (0.0556 * X) + ( -0.2040 * Y) + ( 1.0570 * Z) return color(R * 255, G * 255, B * 255) end --Basic matrix shells -- X = (0 * R) + (0 * G) + (0 * B) -- Y = (0 * R) + (0 * G) + (0 * B) -- Z = (0 * R) + (0 * G) + (0 * B) -- R = (0 * X) + (0 * Y) + (0 * Z) -- G = (0 * X) + (0 * Y) + (0 * Z) -- B = (0 * X) + (0 * Y) + (0 * Z) --The conversion for D65 RGB to D65 XYZ uses the matrix on page 14, ITU-R BT.709 Primaries. --D65 XYZ means XYZ without changing the illuminant. -- XYZD65 -> RGBD65 -- X = 0.4124 0.3576 0.1805 R -- Y = 0.2126 0.7152 0.0722 G -- Z = 0.0193 0.1192 0.9505 B on XYZ2RGB (X, Y, Z) X = X/100.0 Y = Y/100.0 Z = Z/100.0 R = (3.240479 * X) + (-1.537150 * Y) + (-0.498535 * Z) G = (-0.969256 * X) + (1.875992 * Y) + (0.041556 * Z) B = (0.055648 * X) + (-0.204043 * Y) + (1.057311 * Z) return color(R * 255, G * 255, B * 255) end on RGB2XYZ (R, G, B) R = R/255.0 G = G/255.0 B = B/255.0 X = (0.412453 * R) + (0.357580 * G) + (0.180423 * B) Y = (0.212671 * R) + (0.715160 * G) + (0.072169 * B) Z = (0.019334 * R) + (0.119193 * G) + (0.950227 * B) return [X * 100, Y * 100, Z * 100] end --The conversion for D65 RGB to D50 XYZ applies additionally (by multiplication) the Bradford --correction, which takes the adaptation of the eyes into account. This correction is an improved --alternative to the Von Kries correction [1]. --Monitors are assumed D65, but for printed paper the standard illuminant is D50. Therefore --this transformation is recommended if the data are used for printing: -- XYZD50 -> RGBD65 -- X = 0.4361 0.3851 0.1431 R -- Y = 0.2225 0.7169 0.0606 G -- Z = 0.0139 0.0971 0.7141 B |
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