ipa: rkisp1: Add Lux algorithm module

Add a lux algorithm module to rkisp1 IPA for estimating the lux level of
an image. This is reported in metadata, as well as saved in the frame
context so that other algorithms (mainly AGC) can use its value. It does
not set any controls.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>

src/ipa/rkisp1/algorithms/lux.cpp

@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board
+ *
+ * lux.cpp - RkISP1 Lux control
+ */
+
+#include "lux.h"
+
+#include <libcamera/base/log.h>
+
+#include <libcamera/control_ids.h>
+
+#include "libipa/histogram.h"
+#include "libipa/lux.h"
+
+/**
+ * \file lux.h
+ */
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+/**
+ * \class Lux
+ * \brief RkISP1 Lux control
+ *
+ * The Lux algorithm is responsible for estimating the lux level of the image.
+ * It doesn't take or generate any controls, but it provides a lux level for
+ * other algorithms (such as AGC) to use.
+ */
+
+/**
+ * \brief Construct an rkisp1 Lux algo module
+ *
+ * The Lux helper is initialized to 65535 as that is the max bin count on the
+ * rkisp1.
+ */
+Lux::Lux()
+	: lux_(65535)
+{
+}
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::init
+ */
+int Lux::init([[maybe_unused]] IPAContext &context, const YamlObject &tuningData)
+{
+	return lux_.parseTuningData(tuningData);
+}
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::process
+ */
+void Lux::process(IPAContext &context,
+		  [[maybe_unused]] const uint32_t frame,
+		  IPAFrameContext &frameContext,
+		  const rkisp1_stat_buffer *stats,
+		  ControlList &metadata)
+{
+	utils::Duration exposureTime = context.configuration.sensor.lineDuration
+				     * frameContext.sensor.exposure;
+	double gain = frameContext.sensor.gain;
+
+	/* \todo Deduplicate the histogram calculation from AGC */
+	const rkisp1_cif_isp_stat *params = &stats->params;
+	Histogram yHist({ params->hist.hist_bins, context.hw->numHistogramBins },
+			[](uint32_t x) { return x >> 4; });
+
+	double lux = lux_.estimateLux(exposureTime, gain, 1.0, yHist);
+	frameContext.lux.lux = lux;
+	metadata.set(controls::Lux, lux);
+}
+
+REGISTER_IPA_ALGORITHM(Lux, "Lux")
+
+} /* namespace ipa::rkisp1::algorithms */
+
+} /* namespace libcamera */

src/ipa/rkisp1/algorithms/lux.h

@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board
+ *
+ * lux.h - RkISP1 Lux control
+ */
+
+#pragma once
+
+#include <sys/types.h>
+
+#include "libipa/lux.h"
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+class Lux : public Algorithm
+{
+public:
+	Lux();
+
+	int init(IPAContext &context, const YamlObject &tuningData) override;
+	void process(IPAContext &context, const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     const rkisp1_stat_buffer *stats,
+		     ControlList &metadata) override;
+
+private:
+	ipa::Lux lux_;
+};
+
+} /* namespace ipa::rkisp1::algorithms */
+} /* namespace libcamera */

src/ipa/rkisp1/algorithms/meson.build

@@ -12,4 +12,5 @@ rkisp1_ipa_algorithms = files([
     'goc.cpp',
     'gsl.cpp',
     'lsc.cpp',
+    'lux.cpp',
 ])

src/ipa/rkisp1/ipa_context.h

@@ -169,6 +169,10 @@ struct IPAFrameContext : public FrameContext {
 	struct {
 		Matrix<float, 3, 3> ccm;
 	} ccm;
+
+	struct {
+		double lux;
+	} lux;
 };
 
 struct IPAContext {