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/* Copyright (c) 1990 Regents of the University of California */ |
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/* Copyright (c) 1998 Silicon Graphics, Inc. */ |
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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static char SCCSid[] = "$SunId$ SGI"; |
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#endif |
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/* |
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#include "color.h" |
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#define MAXGSHIFT 15 /* maximum shift for gamma table */ |
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#define NULL 0 |
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static BYTE g_mant[256], g_nexp[256]; |
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extern char *bmalloc(); |
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static BYTE g_bval[MAXGSHIFT+1][256]; |
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#define MAXGSHIFT 31 /* maximum shift for gamma table */ |
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static BYTE *g_mant = NULL, *g_nexp = NULL; |
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setcolrgam(g) /* set gamma conversion */ |
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double g; |
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static BYTE (*g_bval)[256] = NULL; |
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#ifndef pow |
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extern double pow(); |
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#endif |
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setcolrcor(f, a2) /* set brightness correction */ |
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double (*f)(); |
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double a2; |
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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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/* allocate tables */ |
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if (g_bval == NULL && (g_bval = |
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(BYTE (*)[256])bmalloc((MAXGSHIFT+1)*256)) == NULL) |
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return(-1); |
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/* compute colr -> gamb mapping */ |
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mult = 1.0/256.0; |
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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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g_bval[i][j] = 256.0 * (*f)((j+.5)*mult, a2); |
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mult *= 0.5; |
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} |
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return(0); |
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} |
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setcolrinv(f, a2) /* set inverse brightness correction */ |
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double (*f)(); |
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double a2; |
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{ |
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double mult; |
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register int i, j; |
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/* allocate tables */ |
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if (g_mant == NULL && (g_mant = (BYTE *)bmalloc(256)) == NULL) |
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return(-1); |
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if (g_nexp == NULL && (g_nexp = (BYTE *)bmalloc(256)) == NULL) |
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return(-1); |
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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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while ((g_mant[j] = mult * pow(j/256.0, g)) < 128) { |
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for (j = 256; j--; ) { |
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while ((g_mant[j] = mult * (*f)((j+.5)/256.0, a2)) < 128) { |
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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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g_mant[0] = 0; |
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g_nexp[0] = COLXS; |
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return(0); |
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} |
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setcolrgam(g) /* set gamma conversion */ |
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double g; |
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{ |
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if (setcolrcor(pow, 1.0/g) < 0) |
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return(-1); |
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return(setcolrinv(pow, g)); |
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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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if (g_bval == NULL) |
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return(-1); |
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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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scan[0][EXP] = COLXS; |
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scan++; |
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} |
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return(0); |
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} |
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{ |
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register int nexpo; |
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if (g_mant == NULL | g_nexp == NULL) |
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return(-1); |
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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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scan[0][EXP] = COLXS - nexpo; |
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scan++; |
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} |
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return(0); |
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} |
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