[PATCH 2/3] ipa: rkisp1: Add Lux algorithm module

[Paul Elder]

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 at ideasonboard.com>
---
 src/ipa/rkisp1/algorithms/lux.cpp     | 76 +++++++++++++++++++++++++++
 src/ipa/rkisp1/algorithms/lux.h       | 39 ++++++++++++++
 src/ipa/rkisp1/algorithms/meson.build |  1 +
 src/ipa/rkisp1/ipa_context.h          |  1 +
 4 files changed, 117 insertions(+)
 create mode 100644 src/ipa/rkisp1/algorithms/lux.cpp
 create mode 100644 src/ipa/rkisp1/algorithms/lux.h

diff --git a/src/ipa/rkisp1/algorithms/lux.cpp b/src/ipa/rkisp1/algorithms/lux.cpp
new file mode 100644
index 00000000..1816ddb2
--- /dev/null
+++ b/src/ipa/rkisp1/algorithms/lux.cpp
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board
+ *
+ * lux.cpp - RkISP1 Lux control
+ */
+
+#include "lux.h"
+
+#include <algorithm>
+#include <cmath>
+
+#include <libcamera/base/log.h>
+
+#include <libcamera/control_ids.h>
+
+#include "libcamera/internal/yaml_parser.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.
+ */
+
+LOG_DEFINE_CATEGORY(RkISP1Lux)
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::init
+ */
+int Lux::init([[maybe_unused]] IPAContext &context, const YamlObject &tuningData)
+{
+	return lux_.readYaml(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;
+
+	const rkisp1_cif_isp_stat *params = &stats->params;
+	Histogram yHist = Histogram(Span<const uint32_t>(params->hist.hist_bins,
+							 context.hw->numHistogramBins), 4);
+
+	/* todo Update this when we support aperture */
+	double lux = lux_.process(gain, exposureTime, 1.0, yHist);
+	frameContext.agc.lux = lux;
+	metadata.set(controls::Lux, lux);
+}
+
+REGISTER_IPA_ALGORITHM(Lux, "Lux")
+
+} /* namespace ipa::rkisp1::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/rkisp1/algorithms/lux.h b/src/ipa/rkisp1/algorithms/lux.h
new file mode 100644
index 00000000..ea98c291
--- /dev/null
+++ b/src/ipa/rkisp1/algorithms/lux.h
@@ -0,0 +1,39 @@
+/* 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 "libcamera/internal/yaml_parser.h"
+
+#include "libipa/lux.h"
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+class Lux : public Algorithm
+{
+public:
+	Lux() = default;
+	~Lux() = default;
+
+	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 */
diff --git a/src/ipa/rkisp1/algorithms/meson.build b/src/ipa/rkisp1/algorithms/meson.build
index c9891e87..b0381d5f 100644
--- a/src/ipa/rkisp1/algorithms/meson.build
+++ b/src/ipa/rkisp1/algorithms/meson.build
@@ -11,4 +11,5 @@ rkisp1_ipa_algorithms = files([
     'filter.cpp',
     'gsl.cpp',
     'lsc.cpp',
+    'lux.cpp',
 ])
diff --git a/src/ipa/rkisp1/ipa_context.h b/src/ipa/rkisp1/ipa_context.h
index dc876da0..c39e0e9b 100644
--- a/src/ipa/rkisp1/ipa_context.h
+++ b/src/ipa/rkisp1/ipa_context.h
@@ -118,6 +118,7 @@ struct IPAFrameContext : public FrameContext {
 		int32_t exposureMode;
 		int32_t constraintMode;
 		utils::Duration maxShutterSpeed;
+		double lux;
 	} agc;
 
 	struct {
-- 
2.39.2