src/common/colrops.c

/* Copyright (c) 1998 Silicon Graphics, Inc. */

#ifndef lint
static char SCCSid[] = "$SunId$ SGI";
#endif

/*
 * Integer operations on COLR scanlines
 */

#include "color.h"

#define NULL            0

extern char     *bmalloc();

#define MAXGSHIFT       31              /* maximum shift for gamma table */

static BYTE     *g_mant = NULL, *g_nexp = NULL;

static BYTE     (*g_bval)[256] = NULL;

#ifndef pow
extern double   pow();
#endif


setcolrcor(f, a2)               /* set brightness correction */
double  (*f)();
double  a2;
{
        double  mult;
        register int    i, j;
                                        /* allocate tables */
        if (g_bval == NULL && (g_bval =
                        (BYTE (*)[256])bmalloc((MAXGSHIFT+1)*256)) == NULL)
                return(-1);
                                        /* compute colr -> gamb mapping */
        mult = 1.0/256.0;
        for (i = 0; i <= MAXGSHIFT; i++) {
                for (j = 0; j < 256; j++)
                        g_bval[i][j] = 256.0 * (*f)((j+.5)*mult, a2);
                mult *= 0.5;
        }
        return(0);
}


setcolrinv(f, a2)               /* set inverse brightness correction */
double  (*f)();
double  a2;
{
        double  mult;
        register int    i, j;
                                        /* allocate tables */
        if (g_mant == NULL && (g_mant = (BYTE *)bmalloc(256)) == NULL)
                return(-1);
        if (g_nexp == NULL && (g_nexp = (BYTE *)bmalloc(256)) == NULL)
                return(-1);
                                        /* compute gamb -> colr mapping */
        i = 0;
        mult = 256.0;
        for (j = 256; j--; ) {
                while ((g_mant[j] = mult * (*f)((j+.5)/256.0, a2)) < 128) {
                        i++;
                        mult *= 2.0;
                }
                g_nexp[j] = i;
        }
        return(0);
}


setcolrgam(g)                   /* set gamma conversion */
double  g;
{
        if (setcolrcor(pow, 1.0/g) < 0)
                return(-1);
        return(setcolrinv(pow, g));
}


colrs_gambs(scan, len)          /* convert scanline of colrs to gamma bytes */
register COLR   *scan;
int     len;
{
        register int    i, expo;

        if (g_bval == NULL)
                return(-1);
        while (len-- > 0) {
                expo = scan[0][EXP] - COLXS;
                if (expo < -MAXGSHIFT) {
                        if (expo < -MAXGSHIFT-8) {
                                scan[0][RED] =
                                scan[0][GRN] =
                                scan[0][BLU] = 0;
                        } else {
                                i = (-MAXGSHIFT-1) - expo;
                                scan[0][RED] = 
                                g_bval[MAXGSHIFT][((scan[0][RED]>>i)+1)>>1];
                                scan[0][GRN] =
                                g_bval[MAXGSHIFT][((scan[0][GRN]>>i)+1)>>1];
                                scan[0][BLU] =
                                g_bval[MAXGSHIFT][((scan[0][BLU]>>i)+1)>>1];
                        }
                } else if (expo > 0) {
                        if (expo > 8) {
                                scan[0][RED] =
                                scan[0][GRN] =
                                scan[0][BLU] = 255;
                        } else {
                                i = (scan[0][RED]<<1 | 1) << (expo-1);
                                scan[0][RED] = i > 255 ? 255 : g_bval[0][i];
                                i = (scan[0][GRN]<<1 | 1) << (expo-1);
                                scan[0][GRN] = i > 255 ? 255 : g_bval[0][i];
                                i = (scan[0][BLU]<<1 | 1) << (expo-1);
                                scan[0][BLU] = i > 255 ? 255 : g_bval[0][i];
                        }
                } else {
                        scan[0][RED] = g_bval[-expo][scan[0][RED]];
                        scan[0][GRN] = g_bval[-expo][scan[0][GRN]];
                        scan[0][BLU] = g_bval[-expo][scan[0][BLU]];
                }
                scan[0][EXP] = COLXS;
                scan++;
        }
        return(0);
}


gambs_colrs(scan, len)          /* convert gamma bytes to colr scanline */
register COLR   *scan;
int     len;
{
        register int    nexpo;

        if (g_mant == NULL | g_nexp == NULL)
                return(-1);
        while (len-- > 0) {
                nexpo = g_nexp[scan[0][RED]];
                if (g_nexp[scan[0][GRN]] < nexpo)
                        nexpo = g_nexp[scan[0][GRN]];
                if (g_nexp[scan[0][BLU]] < nexpo)
                        nexpo = g_nexp[scan[0][BLU]];
                if (nexpo < g_nexp[scan[0][RED]])
                        scan[0][RED] = g_mant[scan[0][RED]]
                                        >> (g_nexp[scan[0][RED]]-nexpo);
                else
                        scan[0][RED] = g_mant[scan[0][RED]];
                if (nexpo < g_nexp[scan[0][GRN]])
                        scan[0][GRN] = g_mant[scan[0][GRN]]
                                        >> (g_nexp[scan[0][GRN]]-nexpo);
                else
                        scan[0][GRN] = g_mant[scan[0][GRN]];
                if (nexpo < g_nexp[scan[0][BLU]])
                        scan[0][BLU] = g_mant[scan[0][BLU]]
                                        >> (g_nexp[scan[0][BLU]]-nexpo);
                else
                        scan[0][BLU] = g_mant[scan[0][BLU]];
                scan[0][EXP] = COLXS - nexpo;
                scan++;
        }
        return(0);
}


shiftcolrs(scan, len, adjust)   /* shift a scanline of colors by 2^adjust */
register COLR   *scan;
register int    len;
register int    adjust;
{
        int     minexp;

        if (adjust == 0)
                return;
        minexp = adjust < 0 ? -adjust : 0;
        while (len-- > 0) {
                if (scan[0][EXP] <= minexp)
                        scan[0][RED] = scan[0][GRN] = scan[0][BLU] =
                        scan[0][EXP] = 0;
                else
                        scan[0][EXP] += adjust;
                scan++;
        }
}


normcolrs(scan, len, adjust)    /* normalize a scanline of colrs */
register COLR  *scan;
int  len;
int  adjust;
{
        register int  c;
        register int  shift;

        while (len-- > 0) {
                shift = scan[0][EXP] + adjust - COLXS;
                if (shift > 0) {
                        if (shift > 8) {
                                scan[0][RED] =
                                scan[0][GRN] =
                                scan[0][BLU] = 255;
                        } else {
                                shift--;
                                c = (scan[0][RED]<<1 | 1) << shift;
                                scan[0][RED] = c > 255 ? 255 : c;
                                c = (scan[0][GRN]<<1 | 1) << shift;
                                scan[0][GRN] = c > 255 ? 255 : c;
                                c = (scan[0][BLU]<<1 | 1) << shift;
                                scan[0][BLU] = c > 255 ? 255 : c;
                        }
                } else if (shift < 0) {
                        if (shift < -8) {
                                scan[0][RED] =
                                scan[0][GRN] =
                                scan[0][BLU] = 0;
                        } else {
                                shift = -1-shift;
                                scan[0][RED] = ((scan[0][RED]>>shift)+1)>>1;
                                scan[0][GRN] = ((scan[0][GRN]>>shift)+1)>>1;
                                scan[0][BLU] = ((scan[0][BLU]>>shift)+1)>>1;
                        }
                }
                scan[0][EXP] = COLXS - adjust;
                scan++;
        }
}
Revision:	2.5
Committed:	Wed Jan 21 12:55:00 1998 UTC (27 years, 9 months ago) by gregl
Content type:	text/plain
Branch:	MAIN
Changes since 2.4:	+4 -6 lines
Log Message:	made conversion from gamma-corrected bytes more robust -- no more zeroes in output
#	User	Rev	Content
1	gregl	2.5	/* Copyright (c) 1998 Silicon Graphics, Inc. */
2	greg	1.1
3			#ifndef lint
4	gregl	2.5	static char SCCSid[] = "$SunId$ SGI";
5	greg	1.1	#endif
6
7			/*
8			* Integer operations on COLR scanlines
9			*/
10
11			#include "color.h"
12
13	greg	2.3	#define NULL 0
14	greg	1.1
15	greg	2.3	extern char *bmalloc();
16	greg	1.1
17	greg	2.3	#define MAXGSHIFT 31 /* maximum shift for gamma table */
18	greg	1.1
19	greg	2.3	static BYTE g_mant = NULL, g_nexp = NULL;
20	greg	1.1
21	greg	2.3	static BYTE (*g_bval)[256] = NULL;
22
23	greg	2.4	#ifndef pow
24	greg	2.3	extern double pow();
25	greg	2.4	#endif
26	greg	2.3
27
28			setcolrcor(f, a2) /* set brightness correction */
29			double (*f)();
30			double a2;
31	greg	1.1	{
32			double mult;
33			register int i, j;
34	greg	2.3	/* allocate tables */
35			if (g_bval == NULL && (g_bval =
36			(BYTE ()[256])bmalloc((MAXGSHIFT+1)256)) == NULL)
37			return(-1);
38	greg	1.1	/* compute colr -> gamb mapping */
39	greg	2.3	mult = 1.0/256.0;
40	greg	1.1	for (i = 0; i <= MAXGSHIFT; i++) {
41			for (j = 0; j < 256; j++)
42	greg	2.3	g_bval[i][j] = 256.0 * (f)((j+.5)mult, a2);
43			mult *= 0.5;
44	greg	1.1	}
45	greg	2.3	return(0);
46			}
47
48
49			setcolrinv(f, a2) /* set inverse brightness correction */
50			double (*f)();
51			double a2;
52			{
53			double mult;
54			register int i, j;
55			/* allocate tables */
56			if (g_mant == NULL && (g_mant = (BYTE *)bmalloc(256)) == NULL)
57			return(-1);
58			if (g_nexp == NULL && (g_nexp = (BYTE *)bmalloc(256)) == NULL)
59			return(-1);
60	greg	1.1	/* compute gamb -> colr mapping */
61			i = 0;
62			mult = 256.0;
63	gregl	2.5	for (j = 256; j--; ) {
64			while ((g_mant[j] = mult * (*f)((j+.5)/256.0, a2)) < 128) {
65	greg	1.1	i++;
66			mult *= 2.0;
67			}
68			g_nexp[j] = i;
69			}
70	greg	2.3	return(0);
71	greg	1.1	}
72
73
74	greg	2.3	setcolrgam(g) /* set gamma conversion */
75			double g;
76			{
77			if (setcolrcor(pow, 1.0/g) < 0)
78			return(-1);
79			return(setcolrinv(pow, g));
80			}
81
82
83	greg	1.1	colrs_gambs(scan, len) /* convert scanline of colrs to gamma bytes */
84			register COLR *scan;
85			int len;
86			{
87			register int i, expo;
88
89	greg	2.3	if (g_bval == NULL)
90			return(-1);
91	greg	1.1	while (len-- > 0) {
92			expo = scan[0][EXP] - COLXS;
93			if (expo < -MAXGSHIFT) {
94			if (expo < -MAXGSHIFT-8) {
95			scan[0][RED] =
96			scan[0][GRN] =
97			scan[0][BLU] = 0;
98			} else {
99			i = (-MAXGSHIFT-1) - expo;
100			scan[0][RED] =
101			g_bval[MAXGSHIFT][((scan[0][RED]>>i)+1)>>1];
102			scan[0][GRN] =
103			g_bval[MAXGSHIFT][((scan[0][GRN]>>i)+1)>>1];
104			scan[0][BLU] =
105			g_bval[MAXGSHIFT][((scan[0][BLU]>>i)+1)>>1];
106			}
107			} else if (expo > 0) {
108			if (expo > 8) {
109			scan[0][RED] =
110			scan[0][GRN] =
111			scan[0][BLU] = 255;
112			} else {
113			i = (scan[0][RED]<<1 \| 1) << (expo-1);
114			scan[0][RED] = i > 255 ? 255 : g_bval[0][i];
115			i = (scan[0][GRN]<<1 \| 1) << (expo-1);
116			scan[0][GRN] = i > 255 ? 255 : g_bval[0][i];
117			i = (scan[0][BLU]<<1 \| 1) << (expo-1);
118			scan[0][BLU] = i > 255 ? 255 : g_bval[0][i];
119			}
120			} else {
121			scan[0][RED] = g_bval[-expo][scan[0][RED]];
122			scan[0][GRN] = g_bval[-expo][scan[0][GRN]];
123			scan[0][BLU] = g_bval[-expo][scan[0][BLU]];
124			}
125			scan[0][EXP] = COLXS;
126			scan++;
127			}
128	greg	2.3	return(0);
129	greg	1.1	}
130
131
132			gambs_colrs(scan, len) /* convert gamma bytes to colr scanline */
133			register COLR *scan;
134			int len;
135			{
136			register int nexpo;
137
138	greg	2.3	if (g_mant == NULL \| g_nexp == NULL)
139			return(-1);
140	greg	1.1	while (len-- > 0) {
141			nexpo = g_nexp[scan[0][RED]];
142			if (g_nexp[scan[0][GRN]] < nexpo)
143			nexpo = g_nexp[scan[0][GRN]];
144			if (g_nexp[scan[0][BLU]] < nexpo)
145			nexpo = g_nexp[scan[0][BLU]];
146			if (nexpo < g_nexp[scan[0][RED]])
147			scan[0][RED] = g_mant[scan[0][RED]]
148			>> (g_nexp[scan[0][RED]]-nexpo);
149			else
150			scan[0][RED] = g_mant[scan[0][RED]];
151			if (nexpo < g_nexp[scan[0][GRN]])
152			scan[0][GRN] = g_mant[scan[0][GRN]]
153			>> (g_nexp[scan[0][GRN]]-nexpo);
154			else
155			scan[0][GRN] = g_mant[scan[0][GRN]];
156			if (nexpo < g_nexp[scan[0][BLU]])
157			scan[0][BLU] = g_mant[scan[0][BLU]]
158			>> (g_nexp[scan[0][BLU]]-nexpo);
159			else
160			scan[0][BLU] = g_mant[scan[0][BLU]];
161			scan[0][EXP] = COLXS - nexpo;
162			scan++;
163			}
164	greg	2.3	return(0);
165	greg	1.1	}
166
167
168			shiftcolrs(scan, len, adjust) /* shift a scanline of colors by 2^adjust */
169			register COLR *scan;
170			register int len;
171			register int adjust;
172			{
173	greg	2.2	int minexp;
174
175			if (adjust == 0)
176			return;
177			minexp = adjust < 0 ? -adjust : 0;
178	greg	1.1	while (len-- > 0) {
179	greg	2.2	if (scan[0][EXP] <= minexp)
180			scan[0][RED] = scan[0][GRN] = scan[0][BLU] =
181			scan[0][EXP] = 0;
182			else
183			scan[0][EXP] += adjust;
184	greg	1.1	scan++;
185			}
186			}
187
188
189			normcolrs(scan, len, adjust) /* normalize a scanline of colrs */
190			register COLR *scan;
191			int len;
192			int adjust;
193			{
194			register int c;
195			register int shift;
196
197			while (len-- > 0) {
198			shift = scan[0][EXP] + adjust - COLXS;
199			if (shift > 0) {
200			if (shift > 8) {
201			scan[0][RED] =
202			scan[0][GRN] =
203			scan[0][BLU] = 255;
204			} else {
205			shift--;
206			c = (scan[0][RED]<<1 \| 1) << shift;
207			scan[0][RED] = c > 255 ? 255 : c;
208			c = (scan[0][GRN]<<1 \| 1) << shift;
209			scan[0][GRN] = c > 255 ? 255 : c;
210			c = (scan[0][BLU]<<1 \| 1) << shift;
211			scan[0][BLU] = c > 255 ? 255 : c;
212			}
213			} else if (shift < 0) {
214			if (shift < -8) {
215			scan[0][RED] =
216			scan[0][GRN] =
217			scan[0][BLU] = 0;
218			} else {
219			shift = -1-shift;
220			scan[0][RED] = ((scan[0][RED]>>shift)+1)>>1;
221			scan[0][GRN] = ((scan[0][GRN]>>shift)+1)>>1;
222			scan[0][BLU] = ((scan[0][BLU]>>shift)+1)>>1;
223			}
224			}
225			scan[0][EXP] = COLXS - adjust;
226			scan++;
227			}
228			}