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root/radiance/ray/src/common/spec_rgb.c
Revision: 2.2
Committed: Fri Mar 5 15:14:04 1993 UTC (31 years, 2 months ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.1: +6 -6 lines
Log Message: 
portability improvements

File Contents

# User Rev Content
1 greg 1.2 /* Copyright (c) 1990 Regents of the University of California */
2    
3 greg 1.1 #ifndef lint
4     static char SCCSid[] = "$SunId$ LBL";
5     #endif
6    
7     /*
8     * Convert colors and spectral ranges.
9     */
10    
11     #include "color.h"
12    
13     /*
14     * The following table contains the CIE tristimulus integrals
15     * for X, Y, and Z. The table is cumulative, so that
16     * each color coordinate integrates to 1.
17     */
18    
19     #define STARTWL 380 /* starting wavelength (nanometers) */
20     #define INCWL 10 /* wavelength increment */
21     #define NINC 40 /* # of values */
22    
23     static BYTE chroma[3][NINC] = {
24     { /* X */
25     0, 0, 0, 2, 6, 13, 22, 30, 36, 41,
26     42, 43, 43, 44, 46, 52, 60, 71, 87, 106,
27     128, 153, 178, 200, 219, 233, 243, 249, 252, 254,
28     255, 255, 255, 255, 255, 255, 255, 255, 255, 255
29     }, { /* Y */
30     0, 0, 0, 0, 0, 1, 2, 4, 7, 11,
31     17, 24, 34, 48, 64, 84, 105, 127, 148, 169,
32     188, 205, 220, 232, 240, 246, 250, 253, 254, 255,
33     255, 255, 255, 255, 255, 255, 255, 255, 255, 255
34     }, { /* Z */
35     0, 0, 2, 10, 32, 66, 118, 153, 191, 220,
36     237, 246, 251, 253, 254, 255, 255, 255, 255, 255,
37     255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
38     255, 255, 255, 255, 255, 255, 255, 255, 255, 255
39     }
40     };
41    
42 greg 1.2 #ifdef NTSC
43 greg 1.3 static float xyz2rgbmat[3][3] = { /* XYZ to RGB (NTSC) */
44 greg 2.2 {1.73, -.48, -.26},
45     {-.81, 1.65, -.02},
46     {.08, -.17, 1.28}
47 greg 1.2 };
48     #else
49     static float xyz2rgbmat[3][3] = { /* XYZ to RGB (color monitor) */
50 greg 2.2 {2.739, -1.145, -.424},
51     {-1.119, 2.029, .033},
52     {.138, -.333, 1.105}
53 greg 1.2 };
54     #endif
55 greg 1.1
56 greg 1.2
57    
58 greg 1.1 spec_rgb(col, s, e) /* compute RGB color from spectral range */
59     COLOR col;
60     int s, e;
61     {
62     COLOR ciecolor;
63    
64     spec_cie(ciecolor, s, e);
65     cie_rgb(col, ciecolor);
66     }
67    
68    
69     spec_cie(col, s, e) /* compute a color from a spectral range */
70     COLOR col; /* returned color */
71     int s, e; /* starting and ending wavelengths */
72     {
73     register int i, d, r;
74    
75     s -= STARTWL;
76     if (s < 0)
77     s = 0;
78    
79     e -= STARTWL;
80 greg 1.2 if (e <= s) {
81     col[RED] = col[GRN] = col[BLU] = 0.0;
82     return;
83     }
84 greg 1.1 if (e >= INCWL*(NINC - 1))
85     e = INCWL*(NINC - 1) - 1;
86    
87     d = e / INCWL; /* interpolate values */
88     r = e % INCWL;
89     for (i = 0; i < 3; i++)
90     col[i] = chroma[i][d]*(INCWL - r) + chroma[i][d + 1]*r;
91    
92     d = s / INCWL;
93     r = s % INCWL;
94     for (i = 0; i < 3; i++)
95     col[i] -= chroma[i][d]*(INCWL - r) - chroma[i][d + 1]*r;
96    
97     col[RED] = (col[RED] + 0.5) / (256*INCWL);
98     col[GRN] = (col[GRN] + 0.5) / (256*INCWL);
99     col[BLU] = (col[BLU] + 0.5) / (256*INCWL);
100     }
101    
102    
103 greg 1.3 cie_rgb(rgbcolor, ciecolor) /* convert CIE to RGB */
104 greg 1.1 register COLOR rgbcolor, ciecolor;
105     {
106     register int i;
107    
108     for (i = 0; i < 3; i++) {
109 greg 1.2 rgbcolor[i] = xyz2rgbmat[i][0]*ciecolor[0] +
110     xyz2rgbmat[i][1]*ciecolor[1] +
111     xyz2rgbmat[i][2]*ciecolor[2] ;
112 greg 1.1 if (rgbcolor[i] < 0.0)
113     rgbcolor[i] = 0.0;
114     }
115     }