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>

1 files changed, 176 insertions, 0 deletions

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 <stdint.h>
+
+#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 &params)
+{
+	// enable adaptive enhancement by default
+	config_.ce_enable = params.get<int>("ce_enable", 1);
+	// the point near the bottom of the histogram to move
+	config_.lo_histogram = params.get<double>("lo_histogram", 0.01);
+	// where in the range to try and move it to
+	config_.lo_level = params.get<double>("lo_level", 0.015);
+	// but don't move by more than this
+	config_.lo_max = params.get<double>("lo_max", 500);
+	// equivalent values for the top of the histogram...
+	config_.hi_histogram = params.get<double>("hi_histogram", 0.95);
+	config_.hi_level = params.get<double>("hi_level", 0.95);
+	config_.hi_max = params.get<double>("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<std::mutex> 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<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);