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/* Copyright (c) 1996 Regents of the University of California */ |
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|
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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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/* |
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* Routines for computing and applying brightness mapping. |
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*/ |
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|
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#include "pcond.h" |
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|
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|
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#define CVRATIO 0.025 /* fraction of pixels allowed > env. */ |
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|
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#define exp10(x) exp(2.302585093*(x)) |
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|
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int modhist[HISTRES]; /* modified histogram */ |
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float cumf[HISTRES+1]; /* cumulative distribution function */ |
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|
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|
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mkcumf() /* make cumulative distribution function */ |
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{ |
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register int i; |
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register long sum; |
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|
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cumf[0] = 0.; |
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sum = modhist[0]; |
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for (i = 1; i < HISTRES; i++) { |
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cumf[i] = (double)sum/histot; |
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sum += modhist[i]; |
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} |
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cumf[HISTRES] = 1.; |
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} |
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|
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|
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double |
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cf(b) /* return cumulative function at b */ |
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double b; |
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{ |
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double x; |
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register int i; |
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|
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i = x = HISTRES*(b - bwmin)/(bwmax - bwmin); |
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x -= (double)i; |
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return(cumf[i]*(1.-x) + cumf[i+1]*x); |
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} |
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|
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|
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double |
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BLw(Lw) /* map world luminance to display brightness */ |
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double Lw; |
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{ |
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double b; |
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|
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if (Lw <= LMIN || (b = Bl(Lw)) <= bwmin+FTINY) |
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return(Bldmin); |
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if (b >= bwmax-FTINY) |
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return(Bldmax); |
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return(Bldmin + cf(Bl(Lw))*(Bldmax-Bldmin)); |
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} |
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|
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|
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double |
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htcontrs(La) /* human threshold contrast sensitivity, dL(La) */ |
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double La; |
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{ |
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double l10La, l10dL; |
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/* formula taken from Ferwerda et al. [SG96] */ |
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if (La < 1.148e-4) |
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return(1.38e-3); |
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l10La = log10(La); |
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if (l10La < -1.44) /* rod response regime */ |
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l10dL = pow(.405*l10La + 1.6, 2.18) - 2.86; |
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else if (l10La < -.0184) |
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l10dL = l10La - .395; |
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else if (l10La < 1.9) /* cone response regime */ |
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l10dL = pow(.249*l10La + .65, 2.7) - .72; |
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else |
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l10dL = l10La - 1.255; |
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|
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return(exp10(l10dL)); |
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} |
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|
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|
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double |
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clampf(Lw) /* derivative clamping function */ |
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double Lw; |
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{ |
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double bLw, ratio; |
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|
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bLw = BLw(Lw); /* apply current brightness map */ |
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ratio = what2do&DO_HSENS ? htcontrs(Lb(bLw))/htcontrs(Lw) : Lb(bLw)/Lw; |
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return(ratio/(Lb1(bLw)*(Bldmax-Bldmin)*Bl1(Lw))); |
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} |
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|
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|
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int |
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shiftdir(bw) /* compute shift direction for histogram */ |
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double bw; |
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{ |
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if (what2do&DO_HSENS && cf(bw) - (bw - bwmin)/(Bldmax - bwmin)) |
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return(1); |
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return(-1); |
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} |
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|
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|
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int |
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mkbrmap() /* make dynamic range map */ |
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{ |
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int hdiffs[HISTRES], above, below; |
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double T, b, s; |
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int maxd, maxi, sd; |
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register int i; |
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/* copy initial histogram */ |
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for (i = 0; i < HISTRES; i++) |
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modhist[i] = bwhist[i]; |
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T = histot * (bwmax - bwmin) / HISTRES; |
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s = (bwmax - bwmin)/HISTRES; |
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/* loop until satisfactory */ |
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for ( ; ; ) { |
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mkcumf(); /* sync brightness mapping */ |
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above = below = 0; /* compute visibility overflow */ |
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for (i = 0, b = bwmin + .5*s; i < HISTRES; i++, b += s) { |
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hdiffs[i] = modhist[i] - (int)(T*clampf(Lb(b)) + .5); |
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if (hdiffs[i] > 0) above += hdiffs[i]; |
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else below -= hdiffs[i]; |
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} |
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if (above <= histot*CVRATIO) |
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break; /* close enough */ |
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if (above-below >= 0) |
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return(-1); /* Houston, we have a problem.... */ |
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/* original looped here as well (BEGIN_L2) */ |
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maxd = 0; /* find largest overvis */ |
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for (i = 0; i < HISTRES; i++) |
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if (hdiffs[i] > maxd) |
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maxd = hdiffs[maxi=i]; |
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/* broke loop here when (maxd == 0) (BREAK_L2) */ |
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for (sd = shiftdir((maxi+.5)/HISTRES*(bwmax-bwmin)+bwmin); |
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hdiffs[maxi] == maxd; sd = -sd) |
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for (i = maxi+sd; i >= 0 & i < HISTRES; i += sd) |
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if (hdiffs[i] < 0) { |
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if (hdiffs[i] <= -maxd) { |
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modhist[i] += maxd; |
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modhist[maxi] -= maxd; |
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hdiffs[i] += maxd; |
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hdiffs[maxi] = 0; |
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} else { |
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modhist[maxi] += hdiffs[i]; |
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modhist[i] -= hdiffs[i]; |
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hdiffs[maxi] += hdiffs[i]; |
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hdiffs[i] = 0; |
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} |
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break; |
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} |
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/* (END_L2) */ |
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} |
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return(0); |
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} |
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|
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|
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scotscan(scan, xres) /* apply scotopic color sensitivity loss */ |
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COLOR *scan; |
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int xres; |
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{ |
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COLOR ctmp; |
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double incolor, b, Lw; |
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register int i; |
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|
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for (i = 0; i < xres; i++) { |
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Lw = plum(scan[i]); |
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if (Lw >= TopMesopic) |
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incolor = 1.; |
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else if (Lw <= BotMesopic) |
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incolor = 0.; |
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else |
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incolor = (Lw - BotMesopic) / |
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(TopMesopic - BotMesopic); |
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if (incolor < 1.-FTINY) { |
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b = (1.-incolor)*slum(scan[i])*inpexp/SWNORM; |
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if (lumf == rgblum) b /= WHTEFFICACY; |
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setcolor(ctmp, b, b, b); |
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if (incolor <= FTINY) |
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setcolor(scan[i], 0., 0., 0.); |
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else |
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scalecolor(scan[i], incolor); |
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addcolor(scan[i], ctmp); |
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} |
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} |
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} |
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|
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|
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mapscan(scan, xres) /* apply tone mapping operator to scanline */ |
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COLOR *scan; |
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int xres; |
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{ |
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double mult, Lw, b; |
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register int i; |
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|
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for (i = 0; i < xres; i++) { |
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Lw = plum(scan[i]); |
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if (Lw < LMIN) { |
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setcolor(scan[i], 0., 0., 0.); |
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continue; |
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} |
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b = BLw(Lw); |
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mult = (Lb(b) - ldmin)/(ldmax - ldmin) / (Lw*inpexp); |
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if (lumf == rgblum) mult *= WHTEFFICACY; |
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scalecolor(scan[i], mult); |
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} |
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} |
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|
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|
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#ifdef DEBUG |
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doplots() /* generate debugging plots */ |
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{ |
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double T, b, s; |
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FILE *fp; |
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char fname[128]; |
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register int i; |
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|
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T = histot * (bwmax - bwmin) / HISTRES; |
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s = (bwmax - bwmin)/HISTRES; |
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|
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sprintf(fname, "%s_hist.plt", infn); |
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if ((fp = fopen(fname, "w")) == NULL) |
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syserror(fname); |
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fputs("include=curve.plt\n", fp); |
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fputs("title=\"Brightness Frequency Distribution\"\n", fp); |
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fprintf(fp, "subtitle=%s\n", infn); |
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fputs("ymin=0\n", fp); |
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fputs("xlabel=\"Perceptual Brightness B(Lw)\"\n", fp); |
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fputs("ylabel=\"Frequency Count\"\n", fp); |
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fputs("Alabel=\"Histogram\"\n", fp); |
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fputs("Alintype=0\n", fp); |
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fputs("Blabel=\"Envelope\"\n", fp); |
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fputs("Bsymsize=0\n", fp); |
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fputs("Adata=\n", fp); |
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for (i = 0, b = bwmin + .5*s; i < HISTRES; i++, b += s) |
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fprintf(fp, "\t%f %d\n", b, modhist[i]); |
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fputs(";\nBdata=\n", fp); |
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for (i = 0, b = bwmin + .5*s; i < HISTRES; i++, b += s) |
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fprintf(fp, "\t%f %f\n", b, T*clampf(Lb(b))); |
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fputs(";\n", fp); |
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fclose(fp); |
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} |
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#endif |
