| 1 |
/* Copyright (c) 1996 Regents of the University of California */ |
| 2 |
|
| 3 |
#ifndef lint |
| 4 |
static char SCCSid[] = "$SunId$ LBL"; |
| 5 |
#endif |
| 6 |
|
| 7 |
/* |
| 8 |
* Routines for computing and applying brightness mapping. |
| 9 |
*/ |
| 10 |
|
| 11 |
#include "pcond.h" |
| 12 |
|
| 13 |
|
| 14 |
#define CVRATIO 0.025 /* fraction of pixels allowed > env. */ |
| 15 |
|
| 16 |
#define BotMesopic 5.62e-3 /* top of scotopic range */ |
| 17 |
#define TopMesopic 5.62 /* bottom of photopic range */ |
| 18 |
|
| 19 |
#define exp10(x) exp(2.302585093*(x)) |
| 20 |
|
| 21 |
int modhist[HISTRES]; /* modified histogram */ |
| 22 |
float cumf[HISTRES+1]; /* cumulative distribution function */ |
| 23 |
|
| 24 |
|
| 25 |
mkcumf() /* make cumulative distribution function */ |
| 26 |
{ |
| 27 |
register int i; |
| 28 |
register long sum; |
| 29 |
|
| 30 |
cumf[0] = 0.; |
| 31 |
sum = modhist[0]; |
| 32 |
for (i = 1; i < HISTRES; i++) { |
| 33 |
cumf[i] = (double)sum/histot; |
| 34 |
sum += modhist[i]; |
| 35 |
} |
| 36 |
cumf[HISTRES] = 1.; |
| 37 |
} |
| 38 |
|
| 39 |
|
| 40 |
double |
| 41 |
cf(b) /* return cumulative function at b */ |
| 42 |
double b; |
| 43 |
{ |
| 44 |
double x; |
| 45 |
register int i; |
| 46 |
|
| 47 |
i = x = HISTRES*(b - bwmin)/(bwmax - bwmin); |
| 48 |
x -= (double)i; |
| 49 |
return(cumf[i]*(1.-x) + cumf[i+1]*x); |
| 50 |
} |
| 51 |
|
| 52 |
|
| 53 |
double |
| 54 |
BLw(Lw) /* map world luminance to display brightness */ |
| 55 |
double Lw; |
| 56 |
{ |
| 57 |
double b; |
| 58 |
|
| 59 |
if (Lw <= LMIN || (b = Bl(Lw)) <= bwmin+FTINY) |
| 60 |
return(Bldmin); |
| 61 |
if (b >= bwmax-FTINY) |
| 62 |
return(Bldmax); |
| 63 |
return(Bldmin + cf(Bl(Lw))*(Bldmax-Bldmin)); |
| 64 |
} |
| 65 |
|
| 66 |
|
| 67 |
double |
| 68 |
htcontrs(La) /* human threshold contrast sensitivity, dL(La) */ |
| 69 |
double La; |
| 70 |
{ |
| 71 |
double l10La, l10dL; |
| 72 |
/* formula taken from Ferwerda et al. [SG96] */ |
| 73 |
if (La < 1.148e-4) |
| 74 |
return(1.38e-3); |
| 75 |
l10La = log10(La); |
| 76 |
if (l10La < -1.44) /* rod response regime */ |
| 77 |
l10dL = pow(.405*l10La + 1.6, 2.18) - 2.86; |
| 78 |
else if (l10La < -.0184) |
| 79 |
l10dL = l10La - .395; |
| 80 |
else if (l10La < 1.9) /* cone response regime */ |
| 81 |
l10dL = pow(.249*l10La + .65, 2.7) - .72; |
| 82 |
else |
| 83 |
l10dL = l10La - 1.255; |
| 84 |
|
| 85 |
return(exp10(l10dL)); |
| 86 |
} |
| 87 |
|
| 88 |
|
| 89 |
double |
| 90 |
clampf(Lw) /* derivative clamping function */ |
| 91 |
double Lw; |
| 92 |
{ |
| 93 |
double bLw, ratio; |
| 94 |
|
| 95 |
bLw = BLw(Lw); /* apply current brightness map */ |
| 96 |
ratio = what2do&DO_HSENS ? htcontrs(Lb(bLw))/htcontrs(Lw) : Lb(bLw)/Lw; |
| 97 |
return(ratio/(Lb1(bLw)*(Bldmax-Bldmin)*Bl1(Lw))); |
| 98 |
} |
| 99 |
|
| 100 |
|
| 101 |
int |
| 102 |
shiftdir(bw) /* compute shift direction for histogram */ |
| 103 |
double bw; |
| 104 |
{ |
| 105 |
if (what2do&DO_HSENS && cf(bw) - (bw - bwmin)/(Bldmax - bwmin)) |
| 106 |
return(1); |
| 107 |
return(-1); |
| 108 |
} |
| 109 |
|
| 110 |
|
| 111 |
int |
| 112 |
mkbrmap() /* make dynamic range map */ |
| 113 |
{ |
| 114 |
int hdiffs[HISTRES], above, below; |
| 115 |
double T, b, s; |
| 116 |
int maxd, maxi, sd; |
| 117 |
register int i; |
| 118 |
/* copy initial histogram */ |
| 119 |
for (i = 0; i < HISTRES; i++) |
| 120 |
modhist[i] = bwhist[i]; |
| 121 |
T = histot * (bwmax - bwmin) / HISTRES; |
| 122 |
s = (bwmax - bwmin)/HISTRES; |
| 123 |
/* loop until satisfactory */ |
| 124 |
for ( ; ; ) { |
| 125 |
mkcumf(); /* sync brightness mapping */ |
| 126 |
above = below = 0; /* compute visibility overflow */ |
| 127 |
for (i = 0, b = bwmin + .5*s; i < HISTRES; i++, b += s) { |
| 128 |
hdiffs[i] = modhist[i] - (int)(T*clampf(Lb(b)) + .5); |
| 129 |
if (hdiffs[i] > 0) above += hdiffs[i]; |
| 130 |
else below -= hdiffs[i]; |
| 131 |
} |
| 132 |
if (above <= histot*CVRATIO) |
| 133 |
break; /* close enough */ |
| 134 |
if (above-below >= 0) |
| 135 |
return(-1); /* Houston, we have a problem.... */ |
| 136 |
/* original looped here as well (BEGIN_L2) */ |
| 137 |
maxd = 0; /* find largest overvis */ |
| 138 |
for (i = 0; i < HISTRES; i++) |
| 139 |
if (hdiffs[i] > maxd) |
| 140 |
maxd = hdiffs[maxi=i]; |
| 141 |
/* broke loop here when (maxd == 0) (BREAK_L2) */ |
| 142 |
for (sd = shiftdir((maxi+.5)/HISTRES*(bwmax-bwmin)+bwmin); |
| 143 |
hdiffs[maxi] == maxd; sd = -sd) |
| 144 |
for (i = maxi+sd; i >= 0 & i < HISTRES; i += sd) |
| 145 |
if (hdiffs[i] < 0) { |
| 146 |
if (hdiffs[i] <= -maxd) { |
| 147 |
modhist[i] += maxd; |
| 148 |
modhist[maxi] -= maxd; |
| 149 |
hdiffs[i] += maxd; |
| 150 |
hdiffs[maxi] = 0; |
| 151 |
} else { |
| 152 |
modhist[maxi] += hdiffs[i]; |
| 153 |
modhist[i] -= hdiffs[i]; |
| 154 |
hdiffs[maxi] += hdiffs[i]; |
| 155 |
hdiffs[i] = 0; |
| 156 |
} |
| 157 |
break; |
| 158 |
} |
| 159 |
/* (END_L2) */ |
| 160 |
} |
| 161 |
return(0); |
| 162 |
} |
| 163 |
|
| 164 |
|
| 165 |
scotscan(scan, xres) /* apply scotopic color sensitivity loss */ |
| 166 |
COLOR *scan; |
| 167 |
int xres; |
| 168 |
{ |
| 169 |
COLOR ctmp; |
| 170 |
double incolor, b, Lw; |
| 171 |
register int i; |
| 172 |
|
| 173 |
for (i = 0; i < xres; i++) { |
| 174 |
Lw = plum(scan[i]); |
| 175 |
if (Lw >= TopMesopic) |
| 176 |
incolor = 1.; |
| 177 |
else if (Lw <= BotMesopic) |
| 178 |
incolor = 0.; |
| 179 |
else |
| 180 |
incolor = (Lw - BotMesopic) / |
| 181 |
(TopMesopic - BotMesopic); |
| 182 |
if (incolor < 1.-FTINY) { |
| 183 |
if (incolor <= FTINY) |
| 184 |
setcolor(scan[i], 0., 0., 0.); |
| 185 |
else |
| 186 |
scalecolor(scan[i], incolor); |
| 187 |
b = (1.-incolor)*slum(scan[i])*inpexp/SWNORM; |
| 188 |
if (lumf == rgblum) b /= WHTEFFICACY; |
| 189 |
setcolor(ctmp, b, b, b); |
| 190 |
addcolor(scan[i], ctmp); |
| 191 |
} |
| 192 |
} |
| 193 |
} |
| 194 |
|
| 195 |
|
| 196 |
mapscan(scan, xres) /* apply tone mapping operator to scanline */ |
| 197 |
COLOR *scan; |
| 198 |
int xres; |
| 199 |
{ |
| 200 |
double mult, Lw, b; |
| 201 |
register int i; |
| 202 |
|
| 203 |
for (i = 0; i < xres; i++) { |
| 204 |
Lw = plum(scan[i]); |
| 205 |
if (Lw < LMIN) { |
| 206 |
setcolor(scan[i], 0., 0., 0.); |
| 207 |
continue; |
| 208 |
} |
| 209 |
b = BLw(Lw); |
| 210 |
mult = (Lb(b) - ldmin)/(ldmax - ldmin) / (Lw*inpexp); |
| 211 |
if (lumf == rgblum) mult *= WHTEFFICACY; |
| 212 |
scalecolor(scan[i], mult); |
| 213 |
} |
| 214 |
} |
| 215 |
|
| 216 |
|
| 217 |
#ifdef DEBUG |
| 218 |
doplots() /* generate debugging plots */ |
| 219 |
{ |
| 220 |
double T, b, s; |
| 221 |
FILE *fp; |
| 222 |
char fname[128]; |
| 223 |
register int i; |
| 224 |
|
| 225 |
T = histot * (bwmax - bwmin) / HISTRES; |
| 226 |
s = (bwmax - bwmin)/HISTRES; |
| 227 |
|
| 228 |
sprintf(fname, "%s_hist.plt", infn); |
| 229 |
if ((fp = fopen(fname, "w")) == NULL) |
| 230 |
syserror(fname); |
| 231 |
fputs("include=curve.plt\n", fp); |
| 232 |
fputs("title=\"Brightness Frequency Distribution\"\n", fp); |
| 233 |
fprintf(fp, "subtitle=%s\n", infn); |
| 234 |
fputs("ymin=0\n", fp); |
| 235 |
fputs("xlabel=\"Perceptual Brightness B(Lw)\"\n", fp); |
| 236 |
fputs("ylabel=\"Frequency Count\"\n", fp); |
| 237 |
fputs("Alabel=\"Histogram\"\n", fp); |
| 238 |
fputs("Alintype=0\n", fp); |
| 239 |
fputs("Blabel=\"Envelope\"\n", fp); |
| 240 |
fputs("Bsymsize=0\n", fp); |
| 241 |
fputs("Adata=\n", fp); |
| 242 |
for (i = 0, b = bwmin + .5*s; i < HISTRES; i++, b += s) |
| 243 |
fprintf(fp, "\t%f %d\n", b, modhist[i]); |
| 244 |
fputs(";\nBdata=\n", fp); |
| 245 |
for (i = 0, b = bwmin + .5*s; i < HISTRES; i++, b += s) |
| 246 |
fprintf(fp, "\t%f %f\n", b, T*clampf(Lb(b))); |
| 247 |
fputs(";\n", fp); |
| 248 |
fclose(fp); |
| 249 |
} |
| 250 |
#endif |
