colorimetry.j

struct ColorSpace
    CIEprimaries::Matrix
    whitepoint::Vector
    rgbxyz::Matrix
    rgbxyzScaled::Matrix
end

function colorspace(xr, yr, xg, yg, xb, yb, xw, yw)
    zr = 1 - (xr+yr)
    zg = 1 - (xg+yg)
    zb = 1 - (xb+yb)
    zw = 1 - (xw+yw)

    rgbxyz = [(yg*zb) - (yb*zg), (xb*zg) - (xg*zb), (xg*yb) - (xb*yg);
              (yb*zr) - (yr*zb), (xr*zb) - (xb*zr), (xb*yr) - (xr*yb);
              (yr*zg) - (yg*zr), (xg*zr) - (xr*zg), (xr*yg) - (xg*yr)]
    mat = [xr, yr, zr;
           xg, yg, zg;
           xb, yb, zb]
    whi = [xw, yw, zw]

    rgbw = rgbxyz*whi ./ yw

    rgbxyzsc = [rgbxyz[1,:] ./ rgbw[1];
                rgbxyz[2,:] ./ rgbw[2];
                rgbxyz[3,:] ./ rgbw[3]]

    return ColorSpace(mat, whi, rgbxyz, rgbxyzsc)
end

CIEsystem = colorspace(0.7355, 0.2645, 0.2658, 0.7243, 0.1669, 0.0085,
                       0.3333, 0.3333)

sRGBsystem = colorspace(.64, .33, .3, .6, .15, .06, .3127, .3290)

rgb(r, g, b) = int32(65535*clamp(r,0,255) +
                     256  *clamp(g,0,255) +
                           clamp(b,0,255))
rgbf(r, g, b) = rgb(255*r, 255*g, 255*b)

function vec2pixel(v)
    w = -min(0, v[1], v[2], v[3])
    if w > 0
        rgbf(v[1]+w, v[2]+w, v[3]+w)
    else
        rgbf(v[1], v[2], v[3])
    end
end

typealias Pixel Int32

redval(p) = div(p,65536)
greenval(p) = div(p,256)%256
blueval(p) = p%256

pixel2vec(p) = [redval(p); greenval(p); blueval(p)]./255

xyz2rgb(sys::ColorSpace, xyz) = sys.rgbxyzScaled * xyz

rgb2yiq(rgb) = [.299, .587, .114;
                .596,-.275,-.321;
                .212,-.523, .311] * rgb

yiq2rgb(yiq) = [1,  .956, .621;
                1, -.272,-.647;
                1,-1.105,1.702] * yiq

rgb2gray(rgb::Vector) = 0.3*v[1] + 0.59*v[2] + 0.11*v[3]
rgb2gray(p::Pixel) =
    do(y = 0.3*redval(p) + 0.59*greenval(p) + 0.11*blueval(p),
       rgb(y,y,y))

cie_color_match =
    [[0.001368, 3.8999999999999999e-005, 0.006450001],
     [0.00150205, 4.2826400000000000e-005, 0.007083216],
     [0.001642328, 4.6914600000000000e-005, 0.007745488],
     [0.001802382, 5.1589599999999998e-005, 0.008501152],
     [0.001995757, 5.7176399999999997e-005, 0.009414544],
     [0.002236, 6.3999999999999997e-005, 0.01054999],
     [0.002535385, 7.2344209999999998e-005, 0.0119658],
     [0.002892603, 8.2212239999999995e-005, 0.01365587],
     [0.003300829, 9.3508159999999998e-005, 0.01558805],
     [0.003753236, 1.0613610000000000e-004, 0.01773015],
     [0.004243, 1.2000000000000000e-004, 0.02005001],
     [0.004762389, 0.000134984, 0.02251136],
     [0.005330048, 0.000151492, 0.02520288],
     [0.005978712, 0.000170208, 0.02827972],
     [0.006741117, 0.000191816, 0.03189704],
     [0.00765, 0.000217, 0.03621],
     [0.008751373, 0.0002469067, 0.04143771],
     [0.01002888, 0.00028124, 0.04750372],
     [0.0114217, 0.00031852, 0.05411988],
     [0.01286901, 0.0003572667, 0.06099803],
     [0.01431, 0.000396, 0.06785001],
     [0.01570443, 0.0004337147, 0.07448632],
     [0.01714744, 0.000473024, 0.08136156],
     [0.01878122, 0.000517876, 0.08915364],
     [0.02074801, 0.0005722187, 0.09854048],
     [0.02319, 0.00064, 0.1102],
     [0.02620736, 0.00072456, 0.1246133],
     [0.02978248, 0.0008255, 0.1417017],
     [0.03388092, 0.00094116, 0.1613035],
     [0.03846824, 0.00106988, 0.1832568],
     [0.04351, 0.00121, 0.2074],
     [0.0489956, 0.001362091, 0.2336921],
     [0.0550226, 0.001530752, 0.2626114],
     [0.0617188, 0.001720368, 0.2947746],
     [0.069212, 0.001935323, 0.3307985],
     [0.07763, 0.00218, 0.3713],
     [0.08695811, 0.0024548, 0.4162091],
     [0.09717672, 0.002764, 0.4654642],
     [0.1084063, 0.0031178, 0.5196948],
     [0.1207672, 0.0035264, 0.5795303000000001],
     [0.13438, 0.004, 0.6456],
     [0.1493582, 0.00454624, 0.7184838],
     [0.1653957, 0.00515932, 0.7967133],
     [0.1819831, 0.00582928, 0.8778459],
     [0.198611, 0.00654616, 0.959439],
     [0.21477, 0.0073, 1.0390501000000001],
     [0.2301868, 0.008086507, 1.1153673],
     [0.2448797, 0.00890872, 1.1884971],
     [0.2587773, 0.00976768, 1.2581233000000001],
     [0.2718079, 0.01066443, 1.3239296],
     [0.2839, 0.0116, 1.3855999999999999],
     [0.2949438, 0.01257317, 1.4426352],
     [0.3048965, 0.01358272, 1.4948035],
     [0.3137873, 0.01462968, 1.5421902999999999],
     [0.3216454, 0.01571509, 1.5848807],
     [0.3285, 0.01684, 1.62296],
     [0.3343513, 0.01800736, 1.6564048],
     [0.3392101, 0.01921448, 1.6852959000000001],
     [0.3431213, 0.02045392, 1.7098745],
     [0.3461296, 0.02171824, 1.7303820999999999],
     [0.34828, 0.023, 1.7470600000000001],
     [0.3495999, 0.02429461, 1.7600446000000001],
     [0.3501474, 0.02561024, 1.7696232999999999],
     [0.350013, 0.02695857, 1.7762636999999999],
     [0.349287, 0.02835125, 1.7804333999999999],
     [0.34806, 0.0298, 1.7826],
     [0.3463733, 0.03131083, 1.7829682],
     [0.3442624, 0.03288368, 1.7816997999999999],
     [0.3418088, 0.03452112, 1.7791982],
     [0.3390941, 0.03622571, 1.7758670999999999],
     [0.3362, 0.038, 1.7721100000000001],
     [0.3331977, 0.03984667, 1.7682589],
     [0.3300411, 0.041768, 1.7640389999999999],
     [0.3266357, 0.043766, 1.7589437999999999],
     [0.3228868, 0.04584267, 1.7524663],
     [0.3187, 0.048, 1.7441],
     [0.3140251, 0.05024368, 1.7335594999999999],
     [0.308884, 0.05257304, 1.7208581000000001],
     [0.3032904, 0.05498056, 1.7059369],
     [0.2972579, 0.05745872, 1.6887372],
     [0.2908, 0.06, 1.6692],
     [0.2839701, 0.06260197, 1.6475287000000001],
     [0.2767214, 0.06527752, 1.6234127],
     [0.2689178, 0.06804208, 1.5960223],
     [0.2604227, 0.07091109, 1.5645279999999999],
     [0.2511, 0.0739, 1.5281],
     [0.2408475, 0.077016, 1.4861114],
     [0.2298512, 0.0802664, 1.4395214999999999],
     [0.2184072, 0.0836668, 1.3898798999999999],
     [0.2068115, 0.0872328, 1.3387362],
     [0.19536, 0.09098, 1.2876399999999999],
     [0.1842136, 0.09491755, 1.2374223],
     [0.1733273, 0.09904584, 1.1878242999999999],
     [0.1626881, 0.1033674, 1.1387611],
     [0.1522833, 0.1078846, 1.0901479999999999],
     [0.1421, 0.1126, 1.0419],
     [0.1321786, 0.117532, 0.9941976],
     [0.1225696, 0.1226744, 0.9473473],
     [0.1132752, 0.1279928, 0.9014531],
     [0.1042979, 0.1334528, 0.8566193],
     [0.09564, 0.13902, 0.8129501],
     [0.08729955, 0.1446764, 0.7705173],
     [0.07930804, 0.1504693, 0.7294448],
     [0.07171776, 0.1564619, 0.6899136],
     [0.06458099, 0.1627177, 0.6521049],
     [0.05795001, 0.1693, 0.6162],
     [0.05186211, 0.1762431, 0.5823286],
     [0.04628152, 0.1835581, 0.5504162],
     [0.04115088, 0.1912735, 0.5203376],
     [0.03641283, 0.199418, 0.4919673],
     [0.03201, 0.20802, 0.46518],
     [0.0279172, 0.2171199, 0.4399246],
     [0.0241444, 0.2267345, 0.4161836],
     [0.020687, 0.2368571, 0.3938822],
     [0.0175404, 0.2474812, 0.3729459],
     [0.0147, 0.2586, 0.3533],
     [0.01216179, 0.2701849, 0.3348578],
     [0.00991996, 0.2822939, 0.3175521],
     [0.00796724, 0.2950505, 0.3013375],
     [0.006296346, 0.308578, 0.2861686],
     [0.0049, 0.323, 0.272],
     [0.003777173, 0.3384021, 0.2588171],
     [0.00294532, 0.3546858, 0.2464838],
     [0.00242488, 0.3716986, 0.2347718],
     [0.002236293, 0.3892875, 0.2234533],
     [0.0024, 0.4073, 0.2123],
     [0.00292552, 0.4256299, 0.2011692],
     [0.00383656, 0.4443096, 0.1901196],
     [0.00517484, 0.4633944, 0.1792254],
     [0.00698208, 0.4829395, 0.1685608],
     [0.0093, 0.503, 0.1582],
     [0.01214949, 0.5235693, 0.1481383],
     [0.01553588, 0.544512, 0.1383758],
     [0.01947752, 0.56569, 0.1289942],
     [0.02399277, 0.5869653, 0.1200751],
     [0.0291, 0.6082, 0.1117],
     [0.03481485, 0.6293456, 0.1039048],
     [0.04112016, 0.6503068, 0.09666748],
     [0.04798504, 0.6708752, 0.08998272],
     [0.05537861, 0.6908424, 0.08384531],
     [0.06327, 0.71, 0.07824999],
     [0.07163501, 0.7281852, 0.07320899],
     [0.08046224, 0.7454636, 0.06867816],
     [0.08973996, 0.7619694, 0.06456784],
     [0.09945645, 0.7778368, 0.06078835],
     [0.1096, 0.7932, 0.05725001],
     [0.1201674, 0.8081104, 0.05390435],
     [0.1311145, 0.8224962, 0.05074664],
     [0.1423679, 0.8363068, 0.04775276],
     [0.1538542, 0.8494916, 0.04489859],
     [0.1655, 0.862, 0.04216],
     [0.1772571, 0.8738108, 0.03950728],
     [0.18914, 0.8849624, 0.03693564],
     [0.2011694, 0.8954936, 0.03445836],
     [0.2133658, 0.9054432, 0.03208872],
     [0.2257499, 0.9148501, 0.02984],
     [0.2383209, 0.9237348, 0.02771181],
     [0.2510668, 0.9320924, 0.02569444],
     [0.2639922, 0.9399226000000001, 0.02378716],
     [0.2771017, 0.9472252, 0.02198925],
     [0.2904, 0.954, 0.0203],
     [0.3038912, 0.9602561, 0.01871805],
     [0.3175726, 0.9660074, 0.01724036],
     [0.3314384, 0.9712606, 0.01586364],
     [0.3454828, 0.9760225, 0.01458461],
     [0.3597, 0.9803, 0.0134],
     [0.3740839, 0.9840924, 0.01230723],
     [0.3886396, 0.9874182, 0.01130188],
     [0.4033784, 0.9903128, 0.01037792],
     [0.4183115, 0.9928116, 0.009529306],
     [0.4334499, 0.9949501, 0.008749999],
     [0.4487953, 0.9967108, 0.0080352],
     [0.464336, 0.9980983, 0.0073816],
     [0.480064, 0.999112, 0.0067854],
     [0.4959713, 0.9997482, 0.0062428],
     [0.5120501, 1.0, 0.005749999],
     [0.5282959, 0.9998567, 0.0053036],
     [0.5446916000000001, 0.9993046, 0.0048998],
     [0.5612094, 0.9983255, 0.0045342],
     [0.5778215, 0.9968987, 0.0042024],
     [0.5945, 0.995, 0.0039],
     [0.6112209, 0.9926005, 0.0036232],
     [0.6279758, 0.9897426, 0.0033706],
     [0.6447602, 0.9864444, 0.0031414],
     [0.6615697, 0.9827241, 0.0029348],
     [0.6784, 0.9786, 0.002749999],
     [0.6952392, 0.9740837, 0.0025852],
     [0.7120586, 0.9691712, 0.0024386],
     [0.7288284, 0.9638568, 0.0023094],
     [0.7455188, 0.9581349, 0.0021968],
     [0.7621, 0.952, 0.0021],
     [0.7785432, 0.9454504, 0.002017733],
     [0.7948256, 0.9384992, 0.0019482],
     [0.8109264000000001, 0.9311628, 0.0018898],
     [0.8268248, 0.9234576, 0.001840933],
     [0.8425, 0.9154, 0.0018],
     [0.8579325, 0.9070064, 0.001766267],
     [0.8730816, 0.8982772, 0.0017378],
     [0.8878944, 0.8892048, 0.0017112],
     [0.9023181, 0.8797816000000001, 0.001683067],
     [0.9163, 0.87, 0.001650001],
     [0.9297995, 0.8598613000000001, 0.001610133],
     [0.9427984, 0.849392, 0.0015644],
     [0.9552776, 0.838622, 0.0015136],
     [0.9672179, 0.8275813, 0.001458533],
     [0.9786, 0.8163, 0.0014],
     [0.9893856, 0.8047947, 0.001336667],
     [0.9995488, 0.793082, 0.00127],
     [1.0090892, 0.781192, 0.001205],
     [1.0180064, 0.7691547, 0.001146667],
     [1.0263, 0.757, 0.0011],
     [1.0339826999999999, 0.7447541, 0.0010688],
     [1.040986, 0.7324224, 0.0010494],
     [1.047188, 0.7200036, 0.0010356],
     [1.0524667000000001, 0.7074965, 0.0010212],
     [1.0567, 0.6949, 0.001],
     [1.0597943999999999, 0.6822192, 0.00096864],
     [1.0617992000000001, 0.6694715999999999, 0.00092992],
     [1.0628067999999999, 0.6566744, 0.00088688],
     [1.0629096, 0.6438448, 0.00084256],
     [1.0622, 0.631, 0.0008],
     [1.0607352000000001, 0.6181555, 0.00076096],
     [1.0584435999999999, 0.6053144, 0.00072368],
     [1.0552244, 0.5924756, 0.00068592],
     [1.0509767999999999, 0.5796379, 0.00064544],
     [1.0456000000000001, 0.5668, 0.0006],
     [1.0390368999999999, 0.5539611, 0.0005478667],
     [1.0313608000000001, 0.5411372, 0.0004916],
     [1.0226662, 0.5283528, 0.0004354],
     [1.0130477, 0.5156323, 0.0003834667],
     [1.0025999999999999, 0.503, 0.00034],
     [0.9913675, 0.4904688, 0.0003072533],
     [0.9793314, 0.4780304, 0.00028316],
     [0.9664916, 0.4656776, 0.00026544],
     [0.9528479, 0.4534032, 0.0002518133],
     [0.9384, 0.4412, 0.00024],
     [0.923194, 0.42908, 0.0002295467],
     [0.9072440000000001, 0.417036, 0.00022064],
     [0.890502, 0.405032, 0.00021196],
     [0.87292, 0.393032, 0.0002021867],
     [0.8544499, 0.381, 0.00019],
     [0.8350840000000001, 0.3689184, 0.0001742133],
     [0.814946, 0.3568272, 0.00015564],
     [0.794186, 0.3447768, 0.00013596],
     [0.772954, 0.3328176, 1.1685329999999999e-004],
     [0.7514, 0.321, 1e-004],
     [0.7295836, 0.3093381, 8.6133330000000006e-005],
     [0.7075888, 0.2978504, 7.4599999999999997e-005],
     [0.6856022000000001, 0.2865936, 6.4999999999999994e-005],
     [0.6638104, 0.2756245, 5.6933330000000001e-005],
     [0.6424, 0.265, 4.9999990000000002e-005],
     [0.6215149, 0.2547632, 4.4159999999999997e-005],
     [0.6011138, 0.2448896, 3.9480000000000001e-005],
     [0.5811052, 0.2353344, 3.5719999999999997e-005],
     [0.5613977, 0.2260528, 3.2639999999999999e-005],
     [0.5419000000000001, 0.217, 3.0000000000000001e-005],
     [0.5225995, 0.2081616, 2.7653330000000000e-005],
     [0.5035464, 0.1995488, 2.5559999999999999e-005],
     [0.4847436, 0.1911552, 2.3640000000000001e-005],
     [0.4661939, 0.1829744, 2.1813329999999999e-005],
     [0.4479, 0.175, 2.0000000000000002e-005],
     [0.4298613, 0.1672235, 1.8133330000000000e-005],
     [0.412098, 0.1596464, 1.6200000000000001e-005],
     [0.394644, 0.1522776, 1.4200000000000000e-005],
     [0.3775333, 0.1451259, 1.2133330000000000e-005],
     [0.3608, 0.1382, 1e-005],
     [0.3444563, 0.1315003, 7.7333329999999996e-006],
     [0.3285168, 0.1250248, 5.4000000000000000e-006],
     [0.3130192, 0.1187792, 3.1999999999999999e-006],
     [0.2980011, 0.1127691, 1.3333330000000001e-006],
     [0.2835, 0.107, 0.0],
     [0.2695448, 0.1014762, 0.0],
     [0.2561184, 0.09618864, 0.0],
     [0.2431896, 0.09112296, 0.0],
     [0.2307272, 0.08626485, 0.0],
     [0.2187, 0.0816, 0.0],
     [0.2070971, 0.07712064, 0.0],
     [0.1959232, 0.07282552, 0.0],
     [0.1851708, 0.06871008, 0.0],
     [0.1748323, 0.06476976, 0.0],
     [0.1649, 0.061, 0.0],
     [0.1553667, 0.05739621, 0.0],
     [0.14623, 0.05395504, 0.0],
     [0.13749, 0.05067376, 0.0],
     [0.1291467, 0.04754965, 0.0],
     [0.1212, 0.04458, 0.0],
     [0.1136397, 0.04175872, 0.0],
     [0.106465, 0.03908496, 0.0],
     [0.09969044, 0.03656384, 0.0],
     [0.09333061, 0.03420048, 0.0],
     [0.0874, 0.032, 0.0],
     [0.08190096, 0.02996261, 0.0],
     [0.07680428, 0.02807664, 0.0],
     [0.07207712, 0.02632936, 0.0],
     [0.06768664, 0.02470805, 0.0],
     [0.0636, 0.0232, 0.0],
     [0.05980685, 0.02180077, 0.0],
     [0.05628216, 0.02050112, 0.0],
     [0.05297104, 0.01928108, 0.0],
     [0.04981861, 0.01812069, 0.0],
     [0.04677, 0.017, 0.0],
     [0.04378405, 0.01590379, 0.0],
     [0.04087536, 0.01483718, 0.0],
     [0.03807264, 0.01381068, 0.0],
     [0.03540461, 0.01283478, 0.0],
     [0.0329, 0.01192, 0.0],
     [0.03056419, 0.01106831, 0.0],
     [0.02838056, 0.01027339, 0.0],
     [0.02634484, 0.009533311, 0.0],
     [0.02445275, 0.008846157, 0.0],
     [0.0227, 0.00821, 0.0],
     [0.02108429, 0.007623781, 0.0],
     [0.01959988, 0.007085424, 0.0],
     [0.01823732, 0.006591476, 0.0],
     [0.01698717, 0.006138485, 0.0],
     [0.01584, 0.005723, 0.0],
     [0.01479064, 0.005343059, 0.0],
     [0.01383132, 0.004995796, 0.0],
     [0.01294868, 0.004676404, 0.0],
     [0.0121292, 0.004380075, 0.0],
     [0.01135916, 0.004102, 0.0],
     [0.01062935, 0.003838453, 0.0],
     [0.009938846, 0.003589099, 0.0],
     [0.009288422, 0.003354219, 0.0],
     [0.008678854, 0.003134093, 0.0],
     [0.008110916, 0.002929, 0.0],
     [0.007582388, 0.002738139, 0.0],
     [0.007088746, 0.002559876, 0.0],
     [0.006627313, 0.002393244, 0.0],
     [0.006195408, 0.002237275, 0.0],
     [0.005790346, 0.002091, 0.0],
     [0.005409826, 0.001953587, 0.0],
     [0.005052583, 0.00182458, 0.0],
     [0.004717512, 0.00170358, 0.0],
     [0.004403507, 0.001590187, 0.0],
     [0.004109457, 0.001484, 0.0],
     [0.003833913, 0.001384496, 0.0],
     [0.003575748, 0.001291268, 0.0],
     [0.003334342, 0.001204092, 0.0],
     [0.003109075, 0.001122744, 0.0],
     [0.002899327, 0.001047, 0.0],
     [0.002704348, 0.0009765896, 0.0],
     [0.00252302, 0.0009111088, 0.0],
     [0.002354168, 0.0008501332, 0.0],
     [0.002196616, 0.0007932384, 0.0],
     [0.00204919, 0.00074, 0.0],
     [0.00191096, 0.0006900827, 0.0],
     [0.001781438, 0.00064331, 0.0],
     [0.00166011, 0.000599496, 0.0],
     [0.001546459, 0.0005584547, 0.0],
     [0.001439971, 0.00052, 0.0],
     [0.001340042, 0.0004839136, 0.0],
     [0.001246275, 0.0004500528, 0.0],
     [0.001158471, 0.0004183452, 0.0],
     [0.00107643, 0.0003887184, 0.0],
     [0.0009999493, 0.0003611, 0.0],
     [0.0009287358, 0.0003353835, 0.0],
     [0.0008624332, 0.0003114404, 0.0],
     [0.0008007503, 0.0002891656, 0.0],
     [0.000743396, 0.0002684539, 0.0],
     [0.0006900786, 0.0002492, 0.0],
     [0.0006405156, 0.0002313019, 0.0],
     [0.0005945021, 0.0002146856, 0.0],
     [0.0005518646, 0.0001992884, 0.0],
     [0.000512429, 0.0001850475, 0.0],
     [0.0004760213, 0.0001719, 0.0],
     [0.0004424536, 0.0001597781, 0.0],
     [0.0004115117, 0.0001486044, 0.0],
     [0.0003829814, 0.0001383016, 0.0],
     [0.0003566491, 0.0001287925, 0.0],
     [0.0003323011, 1.2000000000000000e-004, 0.0],
     [0.0003097586, 1.1185950000000000e-004, 0.0],
     [0.0002888871, 1.0432240000000000e-004, 0.0],
     [0.0002695394, 9.7335600000000004e-005, 0.0],
     [0.0002515682, 9.0845869999999995e-005, 0.0],
     [0.0002348261, 8.4800000000000001e-005, 0.0],
     [0.000219171, 7.9146669999999997e-005, 0.0],
     [0.0002045258, 7.3857999999999997e-005, 0.0],
     [0.0001908405, 6.8916000000000002e-005, 0.0],
     [0.0001780654, 6.4302670000000001e-005, 0.0],
     [0.0001661505, 6.0000000000000002e-005, 0.0],
     [0.0001550236, 5.5981869999999998e-005, 0.0],
     [0.0001446219, 5.2225599999999997e-005, 0.0],
     [0.0001349098, 4.8718399999999998e-005, 0.0],
     [0.000125852, 4.5447469999999999e-005, 0.0],
     [1.1741300000000000e-004, 4.2400000000000001e-005, 0.0],
     [1.0955150000000000e-004, 3.9561039999999999e-005, 0.0],
     [1.0222450000000000e-004, 3.6915120000000003e-005, 0.0],
     [9.5394450000000006e-005, 3.4448680000000000e-005, 0.0],
     [8.9023900000000000e-005, 3.2148160000000002e-005, 0.0],
     [8.3075270000000005e-005, 3.0000000000000001e-005, 0.0],
     [7.7512689999999993e-005, 2.7991250000000001e-005, 0.0],
     [7.2313040000000000e-005, 2.6113560000000001e-005, 0.0],
     [6.7457780000000002e-005, 2.4360240000000000e-005, 0.0],
     [6.2928439999999995e-005, 2.2724610000000000e-005, 0.0],
     [5.8706519999999999e-005, 2.1200000000000000e-005, 0.0],
     [5.4770279999999998e-005, 1.9778550000000001e-005, 0.0],
     [5.1099179999999999e-005, 1.8452850000000001e-005, 0.0],
     [4.7676539999999999e-005, 1.7216869999999999e-005, 0.0],
     [4.4485669999999998e-005, 1.6064590000000001e-005, 0.0],
     [4.1509940000000003e-005, 1.4990000000000000e-005, 0.0]]

# compute the perceived color of a spectral distribution function
function spectrum2xyz(intensity::Function)
    Me = [ intensity(i) | i=380:780 ]
    X = dot(Me, cie_color_match[1, :])
    Y = dot(Me, cie_color_match[2, :])
    Z = dot(Me, cie_color_match[3, :])
    [X; Y; Z] ./ (X+Y+Z)
end

# convert a wavelength to an RGB approximation of its appearance
function wavelength2rgb(lambda::Real)
    idx = lambda - 380 + 1
    frac = idx - truncate(idx)
    idx = truncate(idx)
    if idx < 1 || idx >= size(cie_color_match,2)
        return [0;0;0]
    end

    xyz = (1-frac)*cie_color_match[:,idx] + frac*cie_color_match[:,idx+1]
    xyz /= 1.25
    xyz2rgb(sRGBsystem, xyz)
end