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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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#define MAXGSHIFT 2 /* maximum shift for gamma table */ |
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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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for (j = 255; j >= 0; j--) { |
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rept: |
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g_mant[j] = mult * pow((j+.5)/256.0, g); |
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if (g_mant[j] < 128) { |
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i++; |
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mult *= 2.0; |
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goto rept; |
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} |
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g_nexp[j] = i; |
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} |
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} |
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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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} |
