libcamera: ipa: Raspberry Pi IPA
Initial implementation of the Raspberry Pi (BCM2835) libcamera IPA and associated libraries. All code is licensed under the BSD-2-Clause terms. Copyright (c) 2019-2020 Raspberry Pi Trading Ltd. Signed-off-by: Naushir Patuck <naush@raspberrypi.com> Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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src/ipa/raspberrypi/controller/rpi/contrast.cpp
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src/ipa/raspberrypi/controller/rpi/contrast.cpp
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/* SPDX-License-Identifier: BSD-2-Clause */
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/*
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* Copyright (C) 2019, Raspberry Pi (Trading) Limited
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*
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* contrast.cpp - contrast (gamma) control algorithm
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*/
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#include <stdint.h>
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#include "../contrast_status.h"
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#include "../histogram.hpp"
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#include "contrast.hpp"
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using namespace RPi;
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// This is a very simple control algorithm which simply retrieves the results of
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// AGC and AWB via their "status" metadata, and applies digital gain to the
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// colour channels in accordance with those instructions. We take care never to
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// apply less than unity gains, as that would cause fully saturated pixels to go
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// off-white.
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#define NAME "rpi.contrast"
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Contrast::Contrast(Controller *controller)
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: ContrastAlgorithm(controller), brightness_(0.0), contrast_(1.0)
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{
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}
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char const *Contrast::Name() const
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{
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return NAME;
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}
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void Contrast::Read(boost::property_tree::ptree const ¶ms)
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{
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// enable adaptive enhancement by default
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config_.ce_enable = params.get<int>("ce_enable", 1);
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// the point near the bottom of the histogram to move
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config_.lo_histogram = params.get<double>("lo_histogram", 0.01);
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// where in the range to try and move it to
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config_.lo_level = params.get<double>("lo_level", 0.015);
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// but don't move by more than this
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config_.lo_max = params.get<double>("lo_max", 500);
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// equivalent values for the top of the histogram...
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config_.hi_histogram = params.get<double>("hi_histogram", 0.95);
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config_.hi_level = params.get<double>("hi_level", 0.95);
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config_.hi_max = params.get<double>("hi_max", 2000);
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config_.gamma_curve.Read(params.get_child("gamma_curve"));
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}
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void Contrast::SetBrightness(double brightness)
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{
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brightness_ = brightness;
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}
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void Contrast::SetContrast(double contrast)
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{
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contrast_ = contrast;
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}
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static void fill_in_status(ContrastStatus &status, double brightness,
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double contrast, Pwl &gamma_curve)
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{
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status.brightness = brightness;
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status.contrast = contrast;
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for (int i = 0; i < CONTRAST_NUM_POINTS - 1; i++) {
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int x = i < 16 ? i * 1024
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: (i < 24 ? (i - 16) * 2048 + 16384
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: (i - 24) * 4096 + 32768);
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status.points[i].x = x;
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status.points[i].y = std::min(65535.0, gamma_curve.Eval(x));
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}
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status.points[CONTRAST_NUM_POINTS - 1].x = 65535;
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status.points[CONTRAST_NUM_POINTS - 1].y = 65535;
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}
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void Contrast::Initialise()
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{
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// Fill in some default values as Prepare will run before Process gets
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// called.
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fill_in_status(status_, brightness_, contrast_, config_.gamma_curve);
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}
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void Contrast::Prepare(Metadata *image_metadata)
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{
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std::unique_lock<std::mutex> lock(mutex_);
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image_metadata->Set("contrast.status", status_);
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}
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Pwl compute_stretch_curve(Histogram const &histogram,
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ContrastConfig const &config)
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{
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Pwl enhance;
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enhance.Append(0, 0);
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// If the start of the histogram is rather empty, try to pull it down a
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// bit.
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double hist_lo = histogram.Quantile(config.lo_histogram) *
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(65536 / NUM_HISTOGRAM_BINS);
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double level_lo = config.lo_level * 65536;
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RPI_LOG("Move histogram point " << hist_lo << " to " << level_lo);
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hist_lo = std::max(
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level_lo,
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std::min(65535.0, std::min(hist_lo, level_lo + config.lo_max)));
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RPI_LOG("Final values " << hist_lo << " -> " << level_lo);
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enhance.Append(hist_lo, level_lo);
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// Keep the mid-point (median) in the same place, though, to limit the
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// apparent amount of global brightness shift.
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double mid = histogram.Quantile(0.5) * (65536 / NUM_HISTOGRAM_BINS);
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enhance.Append(mid, mid);
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// If the top to the histogram is empty, try to pull the pixel values
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// there up.
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double hist_hi = histogram.Quantile(config.hi_histogram) *
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(65536 / NUM_HISTOGRAM_BINS);
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double level_hi = config.hi_level * 65536;
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RPI_LOG("Move histogram point " << hist_hi << " to " << level_hi);
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hist_hi = std::min(
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level_hi,
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std::max(0.0, std::max(hist_hi, level_hi - config.hi_max)));
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RPI_LOG("Final values " << hist_hi << " -> " << level_hi);
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enhance.Append(hist_hi, level_hi);
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enhance.Append(65535, 65535);
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return enhance;
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}
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Pwl apply_manual_contrast(Pwl const &gamma_curve, double brightness,
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double contrast)
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{
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Pwl new_gamma_curve;
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RPI_LOG("Manual brightness " << brightness << " contrast " << contrast);
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gamma_curve.Map([&](double x, double y) {
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new_gamma_curve.Append(
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x, std::max(0.0, std::min(65535.0,
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(y - 32768) * contrast +
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32768 + brightness)));
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});
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return new_gamma_curve;
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}
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void Contrast::Process(StatisticsPtr &stats, Metadata *image_metadata)
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{
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(void)image_metadata;
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double brightness = brightness_, contrast = contrast_;
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Histogram histogram(stats->hist[0].g_hist, NUM_HISTOGRAM_BINS);
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// We look at the histogram and adjust the gamma curve in the following
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// ways: 1. Adjust the gamma curve so as to pull the start of the
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// histogram down, and possibly push the end up.
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Pwl gamma_curve = config_.gamma_curve;
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if (config_.ce_enable) {
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if (config_.lo_max != 0 || config_.hi_max != 0)
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gamma_curve = compute_stretch_curve(histogram, config_)
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.Compose(gamma_curve);
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// We could apply other adjustments (e.g. partial equalisation)
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// based on the histogram...?
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}
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// 2. Finally apply any manually selected brightness/contrast
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// adjustment.
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if (brightness != 0 || contrast != 1.0)
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gamma_curve = apply_manual_contrast(gamma_curve, brightness,
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contrast);
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// And fill in the status for output. Use more points towards the bottom
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// of the curve.
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ContrastStatus status;
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fill_in_status(status, brightness, contrast, gamma_curve);
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{
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std::unique_lock<std::mutex> lock(mutex_);
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status_ = status;
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}
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}
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// Register algorithm with the system.
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static Algorithm *Create(Controller *controller)
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{
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return (Algorithm *)new Contrast(controller);
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}
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static RegisterAlgorithm reg(NAME, &Create);
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