[PATCH v5 07/10] libcamera: software_isp: Add CCM algorithm

[Milan Zamazal]

This patch adds color correction matrix (CCM) algorithm to software ISP.
It is based on the corresponding algorithm in rkisp1.

The primary difference against hardware pipelines is that applying the
CCM is optional.  Applying CCM causes a significant slowdown, time
needed to process a frame raises by 40-90% on tested platforms.  If CCM
is really needed, it can be applied, if not, it's better to stick
without it.  This can be configured by presence or omission of Ccm
algorithm in the tuning file.

CCM is changed only if the determined temperature changes by at least
100 K (an arbitrarily selected value), to avoid recomputing the matrices
and lookup tables all the time.

The outputs of the algorithm are not used yet, they will be enabled in
followup patches.

Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/ipa/simple/algorithms/ccm.cpp     | 79 +++++++++++++++++++++++++++
 src/ipa/simple/algorithms/ccm.h       | 43 +++++++++++++++
 src/ipa/simple/algorithms/meson.build |  1 +
 src/ipa/simple/ipa_context.h          | 12 ++++
 4 files changed, 135 insertions(+)
 create mode 100644 src/ipa/simple/algorithms/ccm.cpp
 create mode 100644 src/ipa/simple/algorithms/ccm.h

diff --git a/src/ipa/simple/algorithms/ccm.cpp b/src/ipa/simple/algorithms/ccm.cpp
new file mode 100644
index 00000000..069a12f8
--- /dev/null
+++ b/src/ipa/simple/algorithms/ccm.cpp
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board
+ * Copyright (C) 2024-2025, Red Hat Inc.
+ *
+ * Color correction matrix
+ */
+
+#include "ccm.h"
+
+#include <libcamera/base/log.h>
+#include <libcamera/base/utils.h>
+
+#include <libcamera/control_ids.h>
+
+namespace {
+
+constexpr unsigned int kTemperatureThreshold = 100;
+
+}
+
+namespace libcamera {
+
+namespace ipa::soft::algorithms {
+
+LOG_DEFINE_CATEGORY(IPASoftCcm)
+
+int Ccm::init([[maybe_unused]] IPAContext &context, const YamlObject &tuningData)
+{
+	int ret = ccm_.readYaml(tuningData["ccms"], "ct", "ccm");
+	if (ret < 0) {
+		LOG(IPASoftCcm, Error)
+			<< "Failed to parse 'ccm' parameter from tuning file.";
+		return ret;
+	}
+
+	return 0;
+}
+
+void Ccm::prepare(IPAContext &context, const uint32_t frame,
+		  IPAFrameContext &frameContext, [[maybe_unused]] DebayerParams *params)
+{
+	const unsigned int ct = context.activeState.awb.temperatureK;
+
+	/* Change CCM only on bigger temperature changes. */
+	if (frame > 0 &&
+	    utils::abs_diff(ct, lastCt_) < kTemperatureThreshold) {
+		frameContext.ccm.ccm = context.activeState.ccm.ccm;
+		context.activeState.ccm.changed = false;
+		return;
+	}
+
+	lastCt_ = ct;
+	Matrix<double, 3, 3> ccm = ccm_.getInterpolated(ct);
+
+	context.activeState.ccm.ccm = ccm;
+	frameContext.ccm.ccm = ccm;
+	context.activeState.ccm.changed = true;
+}
+
+void Ccm::process([[maybe_unused]] IPAContext &context,
+		  [[maybe_unused]] const uint32_t frame,
+		  IPAFrameContext &frameContext,
+		  [[maybe_unused]] const SwIspStats *stats,
+		  ControlList &metadata)
+{
+	float m[9];
+	for (unsigned int i = 0; i < 3; i++) {
+		for (unsigned int j = 0; j < 3; j++)
+			m[i * 3 + j] = frameContext.ccm.ccm[i][j];
+	}
+	metadata.set(controls::ColourCorrectionMatrix, m);
+}
+
+REGISTER_IPA_ALGORITHM(Ccm, "Ccm")
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/simple/algorithms/ccm.h b/src/ipa/simple/algorithms/ccm.h
new file mode 100644
index 00000000..e5dc6506
--- /dev/null
+++ b/src/ipa/simple/algorithms/ccm.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024-2025, Red Hat Inc.
+ *
+ * Color correction matrix
+ */
+
+#pragma once
+
+#include "libcamera/internal/matrix.h"
+
+#include <libipa/interpolator.h>
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::soft::algorithms {
+
+class Ccm : public Algorithm
+{
+public:
+	Ccm() = default;
+	~Ccm() = default;
+
+	int init(IPAContext &context, const YamlObject &tuningData) override;
+	void prepare(IPAContext &context,
+		     const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     DebayerParams *params) override;
+	void process(IPAContext &context, const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     const SwIspStats *stats,
+		     ControlList &metadata) override;
+
+private:
+	unsigned int lastCt_;
+	Interpolator<Matrix<double, 3, 3>> ccm_;
+};
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/simple/algorithms/meson.build b/src/ipa/simple/algorithms/meson.build
index 37a2eb53..2d0adb05 100644
--- a/src/ipa/simple/algorithms/meson.build
+++ b/src/ipa/simple/algorithms/meson.build
@@ -4,5 +4,6 @@ soft_simple_ipa_algorithms = files([
     'awb.cpp',
     'agc.cpp',
     'blc.cpp',
+    'ccm.cpp',
     'lut.cpp',
 ])
diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
index df0552db..bd6c66d8 100644
--- a/src/ipa/simple/ipa_context.h
+++ b/src/ipa/simple/ipa_context.h
@@ -13,6 +13,8 @@
 
 #include <libcamera/controls.h>
 
+#include "libcamera/internal/matrix.h"
+
 #include <libipa/fc_queue.h>
 #include <libipa/vector.h>
 
@@ -47,6 +49,12 @@ struct IPAActiveState {
 		uint8_t blackLevel;
 		double contrast;
 	} gamma;
+
+	struct {
+		Matrix<double, 3, 3> ccm;
+		bool changed;
+	} ccm;
+
 	struct {
 		/* 0..2 range, 1.0 = normal */
 		std::optional<double> contrast;
@@ -54,6 +62,10 @@ struct IPAActiveState {
 };
 
 struct IPAFrameContext : public FrameContext {
+	struct {
+		Matrix<double, 3, 3> ccm;
+	} ccm;
+
 	struct {
 		int32_t exposure;
 		double gain;
-- 
2.48.1