libcamera: software_isp: Add CCM algorithm

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.

Since the CCM is float, rather than double, to use the same type as in
the rkisp1 pipeline, the type of color gains is changed from double to
float.

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

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/simple/algorithms/awb.cpp

@@ -59,9 +59,9 @@ void Awb::process(IPAContext &context,
 	 */
 	auto &gains = context.activeState.awb.gains;
 	gains = { {
-		sumR <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumR,
+		sumR <= sumG / 4 ? 4.0f : static_cast<float>(sumG) / sumR,
 		1.0,
-		sumB <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumB,
+		sumB <= sumG / 4 ? 4.0f : static_cast<float>(sumG) / sumB,
 	} };
 
 	RGB<double> rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };

src/ipa/simple/algorithms/ccm.cpp

@@ -0,0 +1,74 @@
+/* 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<float, 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)
+{
+	metadata.set(controls::ColourCorrectionMatrix, frameContext.ccm.ccm.data());
+}
+
+REGISTER_IPA_ALGORITHM(Ccm, "Ccm")
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */

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<float, 3, 3>> ccm_;
+};
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */

src/ipa/simple/algorithms/lut.cpp

@@ -103,7 +103,7 @@ void Lut::prepare(IPAContext &context,
 		const double div = static_cast<double>(DebayerParams::kRGBLookupSize) /
 				   gammaTableSize;
 		/* Apply gamma after gain! */
-		const RGB<double> lutGains = (gains * i / div).min(gammaTableSize - 1);
+		const RGB<float> lutGains = (gains * i / div).min(gammaTableSize - 1);
 		params->red[i] = gammaTable[static_cast<unsigned int>(lutGains.r())];
 		params->green[i] = gammaTable[static_cast<unsigned int>(lutGains.g())];
 		params->blue[i] = gammaTable[static_cast<unsigned int>(lutGains.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',
 ])

src/ipa/simple/ipa_context.h

@@ -13,6 +13,7 @@
 
 #include <libcamera/controls.h>
 
+#include "libcamera/internal/matrix.h"
 #include "libcamera/internal/vector.h"
 
 #include <libipa/fc_queue.h>
@@ -38,7 +39,7 @@ struct IPAActiveState {
 	} blc;
 
 	struct {
-		RGB<double> gains;
+		RGB<float> gains;
 		unsigned int temperatureK;
 	} awb;
 
@@ -48,6 +49,12 @@ struct IPAActiveState {
 		uint8_t blackLevel;
 		double contrast;
 	} gamma;
+
+	struct {
+		Matrix<float, 3, 3> ccm;
+		bool changed;
+	} ccm;
+
 	struct {
 		/* 0..2 range, 1.0 = normal */
 		std::optional<double> contrast;
@@ -55,6 +62,10 @@ struct IPAActiveState {
 };
 
 struct IPAFrameContext : public FrameContext {
+	struct {
+		Matrix<float, 3, 3> ccm;
+	} ccm;
+
 	struct {
 		int32_t exposure;
 		double gain;