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greg |
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/* Copyright (c) 1990 Regents of the University of California */
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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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* Integer operations on COLR scanlines
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*/
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#include "color.h"
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greg |
1.3 |
#define MAXGSHIFT 15 /* maximum shift for gamma table */
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greg |
1.1 |
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static BYTE g_mant[256], g_nexp[256];
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static BYTE g_bval[MAXGSHIFT+1][256];
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setcolrgam(g) /* set gamma conversion */
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double g;
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{
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extern double pow();
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double mult;
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register int i, j;
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/* compute colr -> gamb mapping */
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for (i = 0; i <= MAXGSHIFT; i++) {
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mult = pow(0.5, (double)(i+8));
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for (j = 0; j < 256; j++)
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g_bval[i][j] = 256.0 * pow((j+.5)*mult, 1.0/g);
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}
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/* compute gamb -> colr mapping */
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i = 0;
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mult = 256.0;
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greg |
1.2 |
for (j = 255; j > 0; j--) {
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while ((g_mant[j] = mult * pow(j/256.0, g)) < 128) {
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greg |
1.1 |
i++;
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mult *= 2.0;
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}
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g_nexp[j] = i;
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}
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greg |
1.2 |
g_mant[0] = 0;
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g_nexp[0] = COLXS;
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greg |
1.1 |
}
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colrs_gambs(scan, len) /* convert scanline of colrs to gamma bytes */
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register COLR *scan;
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int len;
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{
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register int i, expo;
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while (len-- > 0) {
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expo = scan[0][EXP] - COLXS;
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if (expo < -MAXGSHIFT) {
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if (expo < -MAXGSHIFT-8) {
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scan[0][RED] =
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scan[0][GRN] =
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scan[0][BLU] = 0;
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} else {
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i = (-MAXGSHIFT-1) - expo;
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scan[0][RED] =
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g_bval[MAXGSHIFT][((scan[0][RED]>>i)+1)>>1];
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scan[0][GRN] =
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g_bval[MAXGSHIFT][((scan[0][GRN]>>i)+1)>>1];
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scan[0][BLU] =
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g_bval[MAXGSHIFT][((scan[0][BLU]>>i)+1)>>1];
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}
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} else if (expo > 0) {
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if (expo > 8) {
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scan[0][RED] =
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scan[0][GRN] =
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scan[0][BLU] = 255;
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} else {
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i = (scan[0][RED]<<1 | 1) << (expo-1);
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scan[0][RED] = i > 255 ? 255 : g_bval[0][i];
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i = (scan[0][GRN]<<1 | 1) << (expo-1);
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scan[0][GRN] = i > 255 ? 255 : g_bval[0][i];
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i = (scan[0][BLU]<<1 | 1) << (expo-1);
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scan[0][BLU] = i > 255 ? 255 : g_bval[0][i];
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}
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} else {
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scan[0][RED] = g_bval[-expo][scan[0][RED]];
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scan[0][GRN] = g_bval[-expo][scan[0][GRN]];
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scan[0][BLU] = g_bval[-expo][scan[0][BLU]];
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}
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scan[0][EXP] = COLXS;
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scan++;
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}
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}
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gambs_colrs(scan, len) /* convert gamma bytes to colr scanline */
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register COLR *scan;
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int len;
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{
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register int nexpo;
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while (len-- > 0) {
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nexpo = g_nexp[scan[0][RED]];
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if (g_nexp[scan[0][GRN]] < nexpo)
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nexpo = g_nexp[scan[0][GRN]];
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if (g_nexp[scan[0][BLU]] < nexpo)
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nexpo = g_nexp[scan[0][BLU]];
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if (nexpo < g_nexp[scan[0][RED]])
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scan[0][RED] = g_mant[scan[0][RED]]
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>> (g_nexp[scan[0][RED]]-nexpo);
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else
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scan[0][RED] = g_mant[scan[0][RED]];
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if (nexpo < g_nexp[scan[0][GRN]])
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scan[0][GRN] = g_mant[scan[0][GRN]]
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>> (g_nexp[scan[0][GRN]]-nexpo);
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else
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scan[0][GRN] = g_mant[scan[0][GRN]];
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if (nexpo < g_nexp[scan[0][BLU]])
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scan[0][BLU] = g_mant[scan[0][BLU]]
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>> (g_nexp[scan[0][BLU]]-nexpo);
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else
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scan[0][BLU] = g_mant[scan[0][BLU]];
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scan[0][EXP] = COLXS - nexpo;
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scan++;
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}
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}
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shiftcolrs(scan, len, adjust) /* shift a scanline of colors by 2^adjust */
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register COLR *scan;
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register int len;
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register int adjust;
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{
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while (len-- > 0) {
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scan[0][EXP] += adjust;
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scan++;
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}
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}
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normcolrs(scan, len, adjust) /* normalize a scanline of colrs */
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register COLR *scan;
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int len;
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int adjust;
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{
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register int c;
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register int shift;
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while (len-- > 0) {
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shift = scan[0][EXP] + adjust - COLXS;
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if (shift > 0) {
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if (shift > 8) {
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scan[0][RED] =
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scan[0][GRN] =
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scan[0][BLU] = 255;
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} else {
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shift--;
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c = (scan[0][RED]<<1 | 1) << shift;
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scan[0][RED] = c > 255 ? 255 : c;
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c = (scan[0][GRN]<<1 | 1) << shift;
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scan[0][GRN] = c > 255 ? 255 : c;
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c = (scan[0][BLU]<<1 | 1) << shift;
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scan[0][BLU] = c > 255 ? 255 : c;
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}
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} else if (shift < 0) {
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if (shift < -8) {
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scan[0][RED] =
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scan[0][GRN] =
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scan[0][BLU] = 0;
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} else {
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shift = -1-shift;
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scan[0][RED] = ((scan[0][RED]>>shift)+1)>>1;
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scan[0][GRN] = ((scan[0][GRN]>>shift)+1)>>1;
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scan[0][BLU] = ((scan[0][BLU]>>shift)+1)>>1;
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}
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}
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scan[0][EXP] = COLXS - adjust;
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scan++;
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}
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}
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