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/* 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);
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