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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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#endif |
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/* |
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* Convert colors and spectral ranges. |
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*/ |
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#include "color.h" |
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/* |
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* The following table contains the CIE tristimulus integrals |
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* for X, Y, and Z. The table is cumulative, so that |
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* each color coordinate integrates to 1. |
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*/ |
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#define STARTWL 380 /* starting wavelength (nanometers) */ |
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#define INCWL 10 /* wavelength increment */ |
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#define NINC 40 /* # of values */ |
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static BYTE chroma[3][NINC] = { |
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{ /* X */ |
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0, 0, 0, 2, 6, 13, 22, 30, 36, 41, |
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42, 43, 43, 44, 46, 52, 60, 71, 87, 106, |
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128, 153, 178, 200, 219, 233, 243, 249, 252, 254, |
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255 |
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}, { /* Y */ |
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0, 0, 0, 0, 0, 1, 2, 4, 7, 11, |
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17, 24, 34, 48, 64, 84, 105, 127, 148, 169, |
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188, 205, 220, 232, 240, 246, 250, 253, 254, 255, |
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255 |
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}, { /* Z */ |
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0, 0, 2, 10, 32, 66, 118, 153, 191, 220, |
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237, 246, 251, 253, 254, 255, 255, 255, 255, 255, |
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, |
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255 |
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} |
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}; |
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spec_rgb(col, s, e) /* compute RGB color from spectral range */ |
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COLOR col; |
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int s, e; |
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{ |
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COLOR ciecolor; |
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spec_cie(ciecolor, s, e); |
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cie_rgb(col, ciecolor); |
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} |
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spec_cie(col, s, e) /* compute a color from a spectral range */ |
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COLOR col; /* returned color */ |
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int s, e; /* starting and ending wavelengths */ |
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{ |
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register int i, d, r; |
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s -= STARTWL; |
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if (s < 0) |
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s = 0; |
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e -= STARTWL; |
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if (e >= INCWL*(NINC - 1)) |
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e = INCWL*(NINC - 1) - 1; |
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d = e / INCWL; /* interpolate values */ |
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r = e % INCWL; |
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for (i = 0; i < 3; i++) |
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col[i] = chroma[i][d]*(INCWL - r) + chroma[i][d + 1]*r; |
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d = s / INCWL; |
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r = s % INCWL; |
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for (i = 0; i < 3; i++) |
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col[i] -= chroma[i][d]*(INCWL - r) - chroma[i][d + 1]*r; |
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col[RED] = (col[RED] + 0.5) / (256*INCWL); |
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col[GRN] = (col[GRN] + 0.5) / (256*INCWL); |
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col[BLU] = (col[BLU] + 0.5) / (256*INCWL); |
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} |
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cie_rgb(rgbcolor, ciecolor) /* convert CIE to RGB (NTSC) */ |
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register COLOR rgbcolor, ciecolor; |
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{ |
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static float cmat[3][3] = { |
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1.73, -.48, -.26, |
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-.81, 1.65, -.02, |
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.08, -.17, 1.28, |
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}; |
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register int i; |
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for (i = 0; i < 3; i++) { |
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rgbcolor[i] = cmat[i][0]*ciecolor[0] + |
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cmat[i][1]*ciecolor[1] + |
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cmat[i][2]*ciecolor[2] ; |
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if (rgbcolor[i] < 0.0) |
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rgbcolor[i] = 0.0; |
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} |
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} |
