src/ipa/raspberrypi/controller/rpi/contrast.cpp


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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 &params)
{
	/* 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_);