1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
/* SPDX-License-Identifier: BSD-2-Clause */
/*
* Copyright (C) 2019, Raspberry Pi (Trading) Limited
*
* contrast.cpp - contrast (gamma) control algorithm
*/
#include <stdint.h>
#include <libcamera/base/log.h>
#include "../contrast_status.h"
#include "../histogram.hpp"
#include "contrast.hpp"
using namespace RPiController;
using namespace libcamera;
LOG_DEFINE_CATEGORY(RPiContrast)
/*
* This is a very simple control algorithm which simply retrieves the results of
* AGC and AWB via their "status" metadata, and applies digital gain to the
* colour channels in accordance with those instructions. We take care never to
* apply less than unity gains, as that would cause fully saturated pixels to go
* off-white.
*/
#define NAME "rpi.contrast"
Contrast::Contrast(Controller *controller)
: ContrastAlgorithm(controller), brightness_(0.0), contrast_(1.0)
{
}
char const *Contrast::name() const
{
return NAME;
}
void Contrast::read(boost::property_tree::ptree const ¶ms)
{
/* enable adaptive enhancement by default */
config_.ceEnable = params.get<int>("ce_enable", 1);
/* the point near the bottom of the histogram to move */
config_.loHistogram = params.get<double>("lo_histogram", 0.01);
/* where in the range to try and move it to */
config_.loLevel = params.get<double>("lo_level", 0.015);
/* but don't move by more than this */
config_.loMax = params.get<double>("lo_max", 500);
/* equivalent values for the top of the histogram... */
config_.hiHistogram = params.get<double>("hi_histogram", 0.95);
config_.hiLevel = params.get<double>("hi_level", 0.95);
config_.hiMax = params.get<double>("hi_max", 2000);
config_.gammaCurve.read(params.get_child("gamma_curve"));
}
void Contrast::setBrightness(double brightness)
{
brightness_ = brightness;
}
void Contrast::setContrast(double contrast)
{
contrast_ = contrast;
}
static void fillInStatus(ContrastStatus &status, double brightness,
double contrast, Pwl &gammaCurve)
{
status.brightness = brightness;
status.contrast = contrast;
for (int i = 0; i < CONTRAST_NUM_POINTS - 1; i++) {
int x = i < 16 ? i * 1024
: (i < 24 ? (i - 16) * 2048 + 16384
: (i - 24) * 4096 + 32768);
status.points[i].x = x;
status.points[i].y = std::min(65535.0, gammaCurve.eval(x));
}
status.points[CONTRAST_NUM_POINTS - 1].x = 65535;
status.points[CONTRAST_NUM_POINTS - 1].y = 65535;
}
void Contrast::initialise()
{
/*
* Fill in some default values as Prepare will run before Process gets
* called.
*/
fillInStatus(status_, brightness_, contrast_, config_.gammaCurve);
}
void Contrast::prepare(Metadata *imageMetadata)
{
std::unique_lock<std::mutex> lock(mutex_);
imageMetadata->set("contrast.status", status_);
}
Pwl computeStretchCurve(Histogram const &histogram,
ContrastConfig const &config)
{
Pwl enhance;
enhance.append(0, 0);
/*
* If the start of the histogram is rather empty, try to pull it down a
* bit.
*/
double histLo = histogram.quantile(config.loHistogram) *
(65536 / NUM_HISTOGRAM_BINS);
double levelLo = config.loLevel * 65536;
LOG(RPiContrast, Debug)
<< "Move histogram point " << histLo << " to " << levelLo;
histLo = std::max(levelLo,
std::min(65535.0, std::min(histLo, levelLo + config.loMax)));
LOG(RPiContrast, Debug)
<< "Final values " << histLo << " -> " << levelLo;
enhance.append(histLo, levelLo);
/*
* Keep the mid-point (median) in the same place, though, to limit the
* apparent amount of global brightness shift.
*/
double mid = histogram.quantile(0.5) * (65536 / NUM_HISTOGRAM_BINS);
enhance.append(mid, mid);
/*
* If the top to the histogram is empty, try to pull the pixel values
* there up.
*/
double histHi = histogram.quantile(config.hiHistogram) *
(65536 / NUM_HISTOGRAM_BINS);
double levelHi = config.hiLevel * 65536;
LOG(RPiContrast, Debug)
<< "Move histogram point " << histHi << " to " << levelHi;
histHi = std::min(levelHi,
std::max(0.0, std::max(histHi, levelHi - config.hiMax)));
LOG(RPiContrast, Debug)
<< "Final values " << histHi << " -> " << levelHi;
enhance.append(histHi, levelHi);
enhance.append(65535, 65535);
return enhance;
}
Pwl applyManualContrast(Pwl const &gammaCurve, double brightness,
double contrast)
{
Pwl newGammaCurve;
LOG(RPiContrast, Debug)
<< "Manual brightness " << brightness << " contrast " << contrast;
gammaCurve.map([&](double x, double y) {
newGammaCurve.append(
x, std::max(0.0, std::min(65535.0,
(y - 32768) * contrast +
32768 + brightness)));
});
return newGammaCurve;
}
void Contrast::process(StatisticsPtr &stats,
[[maybe_unused]] Metadata *imageMetadata)
{
Histogram histogram(stats->hist[0].g_hist, NUM_HISTOGRAM_BINS);
/*
* We look at the histogram and adjust the gamma curve in the following
* ways: 1. Adjust the gamma curve so as to pull the start of the
* histogram down, and possibly push the end up.
*/
Pwl gammaCurve = config_.gammaCurve;
if (config_.ceEnable) {
if (config_.loMax != 0 || config_.hiMax != 0)
gammaCurve = computeStretchCurve(histogram, config_).compose(gammaCurve);
/*
* We could apply other adjustments (e.g. partial equalisation)
* based on the histogram...?
*/
}
/*
* 2. Finally apply any manually selected brightness/contrast
* adjustment.
*/
if (brightness_ != 0 || contrast_ != 1.0)
gammaCurve = applyManualContrast(gammaCurve, brightness_, contrast_);
/*
* And fill in the status for output. Use more points towards the bottom
* of the curve.
*/
ContrastStatus status;
fillInStatus(status, brightness_, contrast_, gammaCurve);
{
std::unique_lock<std::mutex> lock(mutex_);
status_ = status;
}
}
/* Register algorithm with the system. */
static Algorithm *create(Controller *controller)
{
return (Algorithm *)new Contrast(controller);
}
static RegisterAlgorithm reg(NAME, &create);
|
