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root/radiance/ray/src/common/color.c
Revision: 1.2
Committed: Wed Mar 15 13:48:37 1989 UTC (35 years, 1 month ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 1.1: +1 -1 lines
Log Message: 
added cast to unsigned value

File Contents

# User Rev Content
1 greg 1.1 /* Copyright (c) 1986 Regents of the University of California */
2    
3     #ifndef lint
4     static char SCCSid[] = "$SunId$ LBL";
5     #endif
6    
7     /*
8     * color.c - routines for color calculations.
9     *
10     * 10/10/85
11     */
12    
13     #include <stdio.h>
14    
15     #include "color.h"
16    
17     #ifdef SPEC_RGB
18     /*
19     * The following table contains the CIE tristimulus integrals
20     * for X, Y, and Z. The table is cumulative, so that
21     * each color coordinate integrates to 1.
22     */
23    
24     #define STARTWL 380 /* starting wavelength (nanometers) */
25     #define INCWL 10 /* wavelength increment */
26     #define NINC 40 /* # of values */
27    
28     static BYTE chroma[3][NINC] = {
29     { /* X */
30     0, 0, 0, 2, 6, 13, 22, 30, 36, 41,
31     42, 43, 43, 44, 46, 52, 60, 71, 87, 106,
32     128, 153, 178, 200, 219, 233, 243, 249, 252, 254,
33     255, 255, 255, 255, 255, 255, 255, 255, 255, 255
34     }, { /* Y */
35     0, 0, 0, 0, 0, 1, 2, 4, 7, 11,
36     17, 24, 34, 48, 64, 84, 105, 127, 148, 169,
37     188, 205, 220, 232, 240, 246, 250, 253, 254, 255,
38     255, 255, 255, 255, 255, 255, 255, 255, 255, 255
39     }, { /* Z */
40     0, 0, 2, 10, 32, 66, 118, 153, 191, 220,
41     237, 246, 251, 253, 254, 255, 255, 255, 255, 255,
42     255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
43     255, 255, 255, 255, 255, 255, 255, 255, 255, 255
44     }
45     };
46    
47    
48     spec_rgb(col, s, e) /* comput RGB color from spectral range */
49     COLOR col;
50     int s, e;
51     {
52     COLOR ciecolor;
53    
54     spec_cie(ciecolor, s, e);
55     cie_rgb(col, ciecolor);
56     }
57    
58    
59     spec_cie(col, s, e) /* compute a color from a spectral range */
60     COLOR col; /* returned color */
61     int s, e; /* starting and ending wavelengths */
62     {
63     register int i, d, r;
64    
65     s -= STARTWL;
66     if (s < 0)
67     s = 0;
68    
69     e -= STARTWL;
70     if (e >= INCWL*(NINC - 1))
71     e = INCWL*(NINC - 1) - 1;
72    
73     d = e / INCWL; /* interpolate values */
74     r = e % INCWL;
75     for (i = 0; i < 3; i++)
76     col[i] = chroma[i][d]*(INCWL - r) + chroma[i][d + 1]*r;
77    
78     d = s / INCWL;
79     r = s % INCWL;
80     for (i = 0; i < 3; i++)
81     col[i] -= chroma[i][d]*(INCWL - r) - chroma[i][d + 1]*r;
82    
83     col[RED] = (col[RED] + 0.5) / (256*INCWL);
84     col[GRN] = (col[GRN] + 0.5) / (256*INCWL);
85     col[BLU] = (col[BLU] + 0.5) / (256*INCWL);
86     }
87    
88    
89     cie_rgb(rgbcolor, ciecolor) /* convert CIE to RGB (NTSC) */
90     register COLOR rgbcolor, ciecolor;
91     {
92     static float cmat[3][3] = {
93     1.73, -.48, -.26,
94     -.81, 1.65, -.02,
95     .08, -.17, 1.28,
96     };
97     register int i;
98    
99     for (i = 0; i < 3; i++) {
100     rgbcolor[i] = cmat[i][0]*ciecolor[0] +
101     cmat[i][1]*ciecolor[1] +
102     cmat[i][2]*ciecolor[2] ;
103     if (rgbcolor[i] < 0.0)
104     rgbcolor[i] = 0.0;
105     }
106     }
107     #endif
108    
109    
110     fwritecolrs(scanline, len, fp) /* write out a colr scanline */
111     register COLR *scanline;
112     int len;
113     register FILE *fp;
114     {
115     COLR lastcolr;
116     int rept;
117    
118     lastcolr[RED] = lastcolr[GRN] = lastcolr[BLU] = 1;
119     lastcolr[EXP] = 0;
120     rept = 0;
121    
122     while (len > 0) {
123     if (scanline[0][EXP] == lastcolr[EXP] &&
124     scanline[0][RED] == lastcolr[RED] &&
125     scanline[0][GRN] == lastcolr[GRN] &&
126     scanline[0][BLU] == lastcolr[BLU])
127     rept++;
128     else {
129     while (rept) { /* write out count */
130     putc(1, fp);
131     putc(1, fp);
132     putc(1, fp);
133     putc(rept & 255, fp);
134     rept >>= 8;
135     }
136     putc(scanline[0][RED], fp); /* new color */
137     putc(scanline[0][GRN], fp);
138     putc(scanline[0][BLU], fp);
139     putc(scanline[0][EXP], fp);
140     copycolr(lastcolr, scanline[0]);
141     rept = 0;
142     }
143     scanline++;
144     len--;
145     }
146     while (rept) { /* write out count */
147     putc(1, fp);
148     putc(1, fp);
149     putc(1, fp);
150     putc(rept & 255, fp);
151     rept >>= 8;
152     }
153     return(ferror(fp) ? -1 : 0);
154     }
155    
156    
157     freadcolrs(scanline, len, fp) /* read in a colr scanline */
158     register COLR *scanline;
159     int len;
160     register FILE *fp;
161     {
162     int rshift;
163     register int i;
164    
165     rshift = 0;
166    
167     while (len > 0) {
168     scanline[0][RED] = getc(fp);
169     scanline[0][GRN] = getc(fp);
170     scanline[0][BLU] = getc(fp);
171     scanline[0][EXP] = getc(fp);
172     if (feof(fp) || ferror(fp))
173     return(-1);
174     if (scanline[0][RED] == 1 &&
175     scanline[0][GRN] == 1 &&
176     scanline[0][BLU] == 1) {
177     for (i = scanline[0][EXP] << rshift; i > 0; i--) {
178     copycolr(scanline[0], scanline[-1]);
179     scanline++;
180     len--;
181     }
182     rshift += 8;
183     } else {
184     scanline++;
185     len--;
186     rshift = 0;
187     }
188     }
189     return(0);
190     }
191    
192    
193     fwritescan(scanline, len, fp) /* write out a scanline */
194     register COLOR *scanline;
195     int len;
196     register FILE *fp;
197     {
198     COLR lastcolr, thiscolr;
199     int rept;
200    
201     lastcolr[RED] = lastcolr[GRN] = lastcolr[BLU] = 1;
202     lastcolr[EXP] = 0;
203     rept = 0;
204    
205     while (len > 0) {
206     setcolr(thiscolr, scanline[0][RED],
207     scanline[0][GRN],
208     scanline[0][BLU]);
209     if (thiscolr[EXP] == lastcolr[EXP] &&
210     thiscolr[RED] == lastcolr[RED] &&
211     thiscolr[GRN] == lastcolr[GRN] &&
212     thiscolr[BLU] == lastcolr[BLU])
213     rept++;
214     else {
215     while (rept) { /* write out count */
216     putc(1, fp);
217     putc(1, fp);
218     putc(1, fp);
219     putc(rept & 255, fp);
220     rept >>= 8;
221     }
222     putc(thiscolr[RED], fp); /* new color */
223     putc(thiscolr[GRN], fp);
224     putc(thiscolr[BLU], fp);
225     putc(thiscolr[EXP], fp);
226     copycolr(lastcolr, thiscolr);
227     rept = 0;
228     }
229     scanline++;
230     len--;
231     }
232     while (rept) { /* write out count */
233     putc(1, fp);
234     putc(1, fp);
235     putc(1, fp);
236     putc(rept & 255, fp);
237     rept >>= 8;
238     }
239     return(ferror(fp) ? -1 : 0);
240     }
241    
242    
243     freadscan(scanline, len, fp) /* read in a scanline */
244     register COLOR *scanline;
245     int len;
246     register FILE *fp;
247     {
248     COLR thiscolr;
249     int rshift;
250     register int i;
251    
252     rshift = 0;
253    
254     while (len > 0) {
255     thiscolr[RED] = getc(fp);
256     thiscolr[GRN] = getc(fp);
257     thiscolr[BLU] = getc(fp);
258     thiscolr[EXP] = getc(fp);
259     if (feof(fp) || ferror(fp))
260     return(-1);
261     if (thiscolr[RED] == 1 &&
262     thiscolr[GRN] == 1 &&
263     thiscolr[BLU] == 1) {
264     for (i = thiscolr[EXP] << rshift; i > 0; i--) {
265     copycolor(scanline[0], scanline[-1]);
266     scanline++;
267     len--;
268     }
269     rshift += 8;
270     } else {
271     colr_color(scanline[0], thiscolr);
272     scanline++;
273     len--;
274     rshift = 0;
275     }
276     }
277     return(0);
278     }
279    
280    
281     setcolr(clr, r, g, b) /* assign a short color value */
282     register COLR clr;
283     double r, g, b;
284     {
285     double frexp();
286     double d;
287     int e;
288    
289     d = r > g ? r : g;
290     if (b > d) d = b;
291    
292     if (d <= 0.0) {
293     clr[RED] = clr[GRN] = clr[BLU] = 0;
294     clr[EXP] = 0;
295     return;
296     }
297    
298     d = frexp(d, &e) * 256.0 / d;
299    
300     clr[RED] = r * d;
301     clr[GRN] = g * d;
302     clr[BLU] = b * d;
303     clr[EXP] = e + COLXS;
304     }
305    
306    
307     colr_color(col, clr) /* convert short to float color */
308     register COLOR col;
309     register COLR clr;
310     {
311     double ldexp(), f;
312    
313     if (clr[EXP] == 0)
314     col[RED] = col[GRN] = col[BLU] = 0.0;
315     else {
316 greg 1.2 f = ldexp(1.0, (int)clr[EXP]-(COLXS+8));
317 greg 1.1 col[RED] = (clr[RED] + 0.5)*f;
318     col[GRN] = (clr[GRN] + 0.5)*f;
319     col[BLU] = (clr[BLU] + 0.5)*f;
320     }
321     }
322    
323    
324     #ifdef FREXP
325     double
326     frexp(x, ip) /* call it paranoia, I've seen the lib version */
327     register double x;
328     int *ip;
329     {
330     int neg;
331     register int i;
332    
333     if (neg = (x < 0.0))
334     x = -x;
335     else if (x == 0.0) {
336     *ip = 0;
337     return(0.0);
338     }
339     if (x < 0.5)
340     for (i = 0; x < 0.5; i--)
341     x *= 2.0;
342     else
343     for (i = 0; x >= 1.0; i++)
344     x /= 2.0;
345     *ip = i;
346     if (neg)
347     return(-x);
348     else
349     return(x);
350     }
351     #endif