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