From 0db2c8dc75e466e7648dc1b95380495c6a126349 Mon Sep 17 00:00:00 2001 From: Naushir Patuck Date: Sun, 3 May 2020 16:48:42 +0100 Subject: 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 Acked-by: Laurent Pinchart Signed-off-by: Laurent Pinchart --- src/ipa/raspberrypi/controller/rpi/contrast.cpp | 176 ++++++++++++++++++++++++ 1 file changed, 176 insertions(+) create mode 100644 src/ipa/raspberrypi/controller/rpi/contrast.cpp (limited to 'src/ipa/raspberrypi/controller/rpi/contrast.cpp') diff --git a/src/ipa/raspberrypi/controller/rpi/contrast.cpp b/src/ipa/raspberrypi/controller/rpi/contrast.cpp new file mode 100644 index 00000000..e4967990 --- /dev/null +++ b/src/ipa/raspberrypi/controller/rpi/contrast.cpp @@ -0,0 +1,176 @@ +/* SPDX-License-Identifier: BSD-2-Clause */ +/* + * Copyright (C) 2019, Raspberry Pi (Trading) Limited + * + * contrast.cpp - contrast (gamma) control algorithm + */ +#include + +#include "../contrast_status.h" +#include "../histogram.hpp" + +#include "contrast.hpp" + +using namespace RPi; + +// 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_.ce_enable = params.get("ce_enable", 1); + // the point near the bottom of the histogram to move + config_.lo_histogram = params.get("lo_histogram", 0.01); + // where in the range to try and move it to + config_.lo_level = params.get("lo_level", 0.015); + // but don't move by more than this + config_.lo_max = params.get("lo_max", 500); + // equivalent values for the top of the histogram... + config_.hi_histogram = params.get("hi_histogram", 0.95); + config_.hi_level = params.get("hi_level", 0.95); + config_.hi_max = params.get("hi_max", 2000); + config_.gamma_curve.Read(params.get_child("gamma_curve")); +} + +void Contrast::SetBrightness(double brightness) +{ + brightness_ = brightness; +} + +void Contrast::SetContrast(double contrast) +{ + contrast_ = contrast; +} + +static void fill_in_status(ContrastStatus &status, double brightness, + double contrast, Pwl &gamma_curve) +{ + 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, gamma_curve.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. + fill_in_status(status_, brightness_, contrast_, config_.gamma_curve); +} + +void Contrast::Prepare(Metadata *image_metadata) +{ + std::unique_lock lock(mutex_); + image_metadata->Set("contrast.status", status_); +} + +Pwl compute_stretch_curve(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 hist_lo = histogram.Quantile(config.lo_histogram) * + (65536 / NUM_HISTOGRAM_BINS); + double level_lo = config.lo_level * 65536; + RPI_LOG("Move histogram point " << hist_lo << " to " << level_lo); + hist_lo = std::max( + level_lo, + std::min(65535.0, std::min(hist_lo, level_lo + config.lo_max))); + RPI_LOG("Final values " << hist_lo << " -> " << level_lo); + enhance.Append(hist_lo, level_lo); + // 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 hist_hi = histogram.Quantile(config.hi_histogram) * + (65536 / NUM_HISTOGRAM_BINS); + double level_hi = config.hi_level * 65536; + RPI_LOG("Move histogram point " << hist_hi << " to " << level_hi); + hist_hi = std::min( + level_hi, + std::max(0.0, std::max(hist_hi, level_hi - config.hi_max))); + RPI_LOG("Final values " << hist_hi << " -> " << level_hi); + enhance.Append(hist_hi, level_hi); + enhance.Append(65535, 65535); + return enhance; +} + +Pwl apply_manual_contrast(Pwl const &gamma_curve, double brightness, + double contrast) +{ + Pwl new_gamma_curve; + RPI_LOG("Manual brightness " << brightness << " contrast " << contrast); + gamma_curve.Map([&](double x, double y) { + new_gamma_curve.Append( + x, std::max(0.0, std::min(65535.0, + (y - 32768) * contrast + + 32768 + brightness))); + }); + return new_gamma_curve; +} + +void Contrast::Process(StatisticsPtr &stats, Metadata *image_metadata) +{ + (void)image_metadata; + double brightness = brightness_, contrast = contrast_; + 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 gamma_curve = config_.gamma_curve; + if (config_.ce_enable) { + if (config_.lo_max != 0 || config_.hi_max != 0) + gamma_curve = compute_stretch_curve(histogram, config_) + .Compose(gamma_curve); + // 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) + gamma_curve = apply_manual_contrast(gamma_curve, brightness, + contrast); + // And fill in the status for output. Use more points towards the bottom + // of the curve. + ContrastStatus status; + fill_in_status(status, brightness, contrast, gamma_curve); + { + std::unique_lock lock(mutex_); + status_ = status; + } +} + +// Register algorithm with the system. +static Algorithm *Create(Controller *controller) +{ + return (Algorithm *)new Contrast(controller); +} +static RegisterAlgorithm reg(NAME, &Create); -- cgit v1.2.1