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/* SPDX-License-Identifier: BSD-2-Clause */
/*
* Copyright (C) 2019, Raspberry Pi Ltd
*
* contrast.cpp - contrast (gamma) control algorithm
*/
#include <stdint.h>
#include <libcamera/base/log.h>
#include "../contrast_status.h"
#include "../histogram.h"
#include "contrast.h"
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;
}
int Contrast::read(const libcamera::YamlObject ¶ms)
{
// enable adaptive enhancement by default
config_.ceEnable = params["ce_enable"].get<int>(1);
ceEnable_ = config_.ceEnable;
// the point near the bottom of the histogram to move
config_.loHistogram = params["lo_histogram"].get<double>(0.01);
// where in the range to try and move it to
config_.loLevel = params["lo_level"].get<double>(0.015);
// but don't move by more than this
config_.loMax = params["lo_max"].get<double>(500);
// equivalent values for the top of the histogram...
config_.hiHistogram = params["hi_histogram"].get<double>(0.95);
config_.hiLevel = params["hi_level"].get<double>(0.95);
config_.hiMax = params["hi_max"].get<double>(2000);
return config_.gammaCurve.read(params["gamma_curve"]);
}
void Contrast::setBrightness(double brightness)
{
brightness_ = brightness;
}
void Contrast::setContrast(double contrast)
{
contrast_ = contrast;
}
void Contrast::enableCe(bool enable)
{
ceEnable_ = enable;
}
void Contrast::restoreCe()
{
ceEnable_ = config_.ceEnable;
}
void Contrast::initialise()
{
/*
* Fill in some default values as Prepare will run before Process gets
* called.
*/
status_.brightness = brightness_;
status_.contrast = contrast_;
status_.gammaCurve = config_.gammaCurve;
}
void Contrast::prepare(Metadata *imageMetadata)
{
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 / 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 / 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 / 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->yHist;
/*
* 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 (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.
*/
status_.brightness = brightness_;
status_.contrast = contrast_;
status_.gammaCurve = std::move(gammaCurve);
}
/* Register algorithm with the system. */
static Algorithm *create(Controller *controller)
{
return (Algorithm *)new Contrast(controller);
}
static RegisterAlgorithm reg(NAME, &create);
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