src/common/colrops.c

/* Copyright (c) 1990 Regents of the University of California */

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

/*
 * Integer operations on COLR scanlines
 */

#include "color.h"

#define MAXGSHIFT       15              /* maximum shift for gamma table */

static BYTE     g_mant[256], g_nexp[256];

static BYTE     g_bval[MAXGSHIFT+1][256];


setcolrgam(g)                   /* set gamma conversion */
double  g;
{
        extern double   pow();
        double  mult;
        register int    i, j;
                                        /* compute colr -> gamb mapping */
        for (i = 0; i <= MAXGSHIFT; i++) {
                mult = pow(0.5, (double)(i+8));
                for (j = 0; j < 256; j++)
                        g_bval[i][j] = 256.0 * pow((j+.5)*mult, 1.0/g);
        }
                                        /* compute gamb -> colr mapping */
        i = 0;
        mult = 256.0;
        for (j = 255; j > 0; j--) {
                while ((g_mant[j] = mult * pow(j/256.0, g)) < 128) {
                        i++;
                        mult *= 2.0;
                }
                g_nexp[j] = i;
        }
        g_mant[0] = 0;
        g_nexp[0] = COLXS;
}


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

        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++;
        }
}


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

        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++;
        }
}


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:	2.2
Committed:	Tue Feb 18 15:25:55 1992 UTC (32 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.1:	+10 -1 lines
Log Message:	bug fix for small exponents in shiftcolrs()
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1990 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Integer operations on COLR scanlines
9			*/
10
11			#include "color.h"
12
13	greg	1.3	#define MAXGSHIFT 15 /* maximum shift for gamma table */
14	greg	1.1
15			static BYTE g_mant[256], g_nexp[256];
16
17			static BYTE g_bval[MAXGSHIFT+1][256];
18
19
20			setcolrgam(g) /* set gamma conversion */
21			double g;
22			{
23			extern double pow();
24			double mult;
25			register int i, j;
26			/* compute colr -> gamb mapping */
27			for (i = 0; i <= MAXGSHIFT; i++) {
28			mult = pow(0.5, (double)(i+8));
29			for (j = 0; j < 256; j++)
30			g_bval[i][j] = 256.0 * pow((j+.5)*mult, 1.0/g);
31			}
32			/* compute gamb -> colr mapping */
33			i = 0;
34			mult = 256.0;
35	greg	1.2	for (j = 255; j > 0; j--) {
36			while ((g_mant[j] = mult * pow(j/256.0, g)) < 128) {
37	greg	1.1	i++;
38			mult *= 2.0;
39			}
40			g_nexp[j] = i;
41			}
42	greg	1.2	g_mant[0] = 0;
43			g_nexp[0] = COLXS;
44	greg	1.1	}
45
46
47			colrs_gambs(scan, len) /* convert scanline of colrs to gamma bytes */
48			register COLR *scan;
49			int len;
50			{
51			register int i, expo;
52
53			while (len-- > 0) {
54			expo = scan[0][EXP] - COLXS;
55			if (expo < -MAXGSHIFT) {
56			if (expo < -MAXGSHIFT-8) {
57			scan[0][RED] =
58			scan[0][GRN] =
59			scan[0][BLU] = 0;
60			} else {
61			i = (-MAXGSHIFT-1) - expo;
62			scan[0][RED] =
63			g_bval[MAXGSHIFT][((scan[0][RED]>>i)+1)>>1];
64			scan[0][GRN] =
65			g_bval[MAXGSHIFT][((scan[0][GRN]>>i)+1)>>1];
66			scan[0][BLU] =
67			g_bval[MAXGSHIFT][((scan[0][BLU]>>i)+1)>>1];
68			}
69			} else if (expo > 0) {
70			if (expo > 8) {
71			scan[0][RED] =
72			scan[0][GRN] =
73			scan[0][BLU] = 255;
74			} else {
75			i = (scan[0][RED]<<1 \| 1) << (expo-1);
76			scan[0][RED] = i > 255 ? 255 : g_bval[0][i];
77			i = (scan[0][GRN]<<1 \| 1) << (expo-1);
78			scan[0][GRN] = i > 255 ? 255 : g_bval[0][i];
79			i = (scan[0][BLU]<<1 \| 1) << (expo-1);
80			scan[0][BLU] = i > 255 ? 255 : g_bval[0][i];
81			}
82			} else {
83			scan[0][RED] = g_bval[-expo][scan[0][RED]];
84			scan[0][GRN] = g_bval[-expo][scan[0][GRN]];
85			scan[0][BLU] = g_bval[-expo][scan[0][BLU]];
86			}
87			scan[0][EXP] = COLXS;
88			scan++;
89			}
90			}
91
92
93			gambs_colrs(scan, len) /* convert gamma bytes to colr scanline */
94			register COLR *scan;
95			int len;
96			{
97			register int nexpo;
98
99			while (len-- > 0) {
100			nexpo = g_nexp[scan[0][RED]];
101			if (g_nexp[scan[0][GRN]] < nexpo)
102			nexpo = g_nexp[scan[0][GRN]];
103			if (g_nexp[scan[0][BLU]] < nexpo)
104			nexpo = g_nexp[scan[0][BLU]];
105			if (nexpo < g_nexp[scan[0][RED]])
106			scan[0][RED] = g_mant[scan[0][RED]]
107			>> (g_nexp[scan[0][RED]]-nexpo);
108			else
109			scan[0][RED] = g_mant[scan[0][RED]];
110			if (nexpo < g_nexp[scan[0][GRN]])
111			scan[0][GRN] = g_mant[scan[0][GRN]]
112			>> (g_nexp[scan[0][GRN]]-nexpo);
113			else
114			scan[0][GRN] = g_mant[scan[0][GRN]];
115			if (nexpo < g_nexp[scan[0][BLU]])
116			scan[0][BLU] = g_mant[scan[0][BLU]]
117			>> (g_nexp[scan[0][BLU]]-nexpo);
118			else
119			scan[0][BLU] = g_mant[scan[0][BLU]];
120			scan[0][EXP] = COLXS - nexpo;
121			scan++;
122			}
123			}
124
125
126			shiftcolrs(scan, len, adjust) /* shift a scanline of colors by 2^adjust */
127			register COLR *scan;
128			register int len;
129			register int adjust;
130			{
131	greg	2.2	int minexp;
132
133			if (adjust == 0)
134			return;
135			minexp = adjust < 0 ? -adjust : 0;
136	greg	1.1	while (len-- > 0) {
137	greg	2.2	if (scan[0][EXP] <= minexp)
138			scan[0][RED] = scan[0][GRN] = scan[0][BLU] =
139			scan[0][EXP] = 0;
140			else
141			scan[0][EXP] += adjust;
142	greg	1.1	scan++;
143			}
144			}
145
146
147			normcolrs(scan, len, adjust) /* normalize a scanline of colrs */
148			register COLR *scan;
149			int len;
150			int adjust;
151			{
152			register int c;
153			register int shift;
154
155			while (len-- > 0) {
156			shift = scan[0][EXP] + adjust - COLXS;
157			if (shift > 0) {
158			if (shift > 8) {
159			scan[0][RED] =
160			scan[0][GRN] =
161			scan[0][BLU] = 255;
162			} else {
163			shift--;
164			c = (scan[0][RED]<<1 \| 1) << shift;
165			scan[0][RED] = c > 255 ? 255 : c;
166			c = (scan[0][GRN]<<1 \| 1) << shift;
167			scan[0][GRN] = c > 255 ? 255 : c;
168			c = (scan[0][BLU]<<1 \| 1) << shift;
169			scan[0][BLU] = c > 255 ? 255 : c;
170			}
171			} else if (shift < 0) {
172			if (shift < -8) {
173			scan[0][RED] =
174			scan[0][GRN] =
175			scan[0][BLU] = 0;
176			} else {
177			shift = -1-shift;
178			scan[0][RED] = ((scan[0][RED]>>shift)+1)>>1;
179			scan[0][GRN] = ((scan[0][GRN]>>shift)+1)>>1;
180			scan[0][BLU] = ((scan[0][BLU]>>shift)+1)>>1;
181			}
182			}
183			scan[0][EXP] = COLXS - adjust;
184			scan++;
185			}
186			}