[libcamera-devel] [PATCH v1 3/6] ipa: rkisp1: Introduce Black Level Correction

[Jean-Michel Hautbois]

In order to have the proper pixel levels, apply a fixed black level
correction, based on the imx219 tuning file in RPi. The value is 4096 on
16 bits, and the pipeline for RkISP1 is on 12 bits, scale it.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
---
 src/ipa/rkisp1/algorithms/blc.cpp     | 55 +++++++++++++++++++++++++++
 src/ipa/rkisp1/algorithms/blc.h       | 30 +++++++++++++++
 src/ipa/rkisp1/algorithms/meson.build |  1 +
 src/ipa/rkisp1/rkisp1.cpp             |  2 +
 4 files changed, 88 insertions(+)
 create mode 100644 src/ipa/rkisp1/algorithms/blc.cpp
 create mode 100644 src/ipa/rkisp1/algorithms/blc.h

diff --git a/src/ipa/rkisp1/algorithms/blc.cpp b/src/ipa/rkisp1/algorithms/blc.cpp
new file mode 100644
index 000000000..f27a8e439
--- /dev/null
+++ b/src/ipa/rkisp1/algorithms/blc.cpp
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Ideas On Board
+ *
+ * blc.cpp - RkISP1 Black Level Correction control
+ */
+
+#include "blc.h"
+
+/**
+ * \file blc.h
+ */
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+/**
+ * \class BlackLevelCorrection
+ * \brief RkISP1 Black Level Correction control
+ *
+ * The pixels output by the camera normally include a black level, because
+ * sensors do not always report a signal level of '0' for black. Pixels at or
+ * below this level should be considered black. To achieve that, the RkISP BLC
+ * algorithm subtracts a configurable offset from all pixels.
+ *
+ * The black level can be measured at runtime from an optical dark region of the
+ * camera sensor, or measured during the camera tuning process. The first option
+ * isn't currently supported.
+ */
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::prepare
+ */
+void BlackLevelCorrection::prepare([[maybe_unused]] IPAContext &context,
+				   rkisp1_params_cfg *params)
+{
+	/*
+	 * Substract fixed values taken from imx219 tuning file.
+	 * \todo Use a configuration file for it ?
+	 */
+	params->others.bls_config.enable_auto = 0;
+	params->others.bls_config.fixed_val.r = 256;
+	params->others.bls_config.fixed_val.gr = 256;
+	params->others.bls_config.fixed_val.gb = 256;
+	params->others.bls_config.fixed_val.b = 256;
+
+	params->module_en_update |= RKISP1_CIF_ISP_MODULE_BLS;
+	params->module_ens |= RKISP1_CIF_ISP_MODULE_BLS;
+	params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_BLS;
+}
+
+} /* namespace ipa::rkisp1::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/rkisp1/algorithms/blc.h b/src/ipa/rkisp1/algorithms/blc.h
new file mode 100644
index 000000000..331a22097
--- /dev/null
+++ b/src/ipa/rkisp1/algorithms/blc.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Ideas On Board
+ *
+ * blc.h - RkISP1 Black Level Correction control
+ */
+
+#pragma once
+
+#include <linux/rkisp1-config.h>
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+struct IPACameraSensorInfo;
+
+namespace ipa::rkisp1::algorithms {
+
+class BlackLevelCorrection : public Algorithm
+{
+public:
+	BlackLevelCorrection() = default;
+	~BlackLevelCorrection() = default;
+
+	void prepare(IPAContext &context, rkisp1_params_cfg *params) override;
+};
+
+} /* namespace ipa::rkisp1::algorithms */
+} /* namespace libcamera */
diff --git a/src/ipa/rkisp1/algorithms/meson.build b/src/ipa/rkisp1/algorithms/meson.build
index 0678518d8..e6767aa5f 100644
--- a/src/ipa/rkisp1/algorithms/meson.build
+++ b/src/ipa/rkisp1/algorithms/meson.build
@@ -2,5 +2,6 @@
 
 rkisp1_ipa_algorithms = files([
     'agc.cpp',
+    'blc.cpp',
     'sdg.cpp',
 ])
diff --git a/src/ipa/rkisp1/rkisp1.cpp b/src/ipa/rkisp1/rkisp1.cpp
index cd425a2e1..ec879ba37 100644
--- a/src/ipa/rkisp1/rkisp1.cpp
+++ b/src/ipa/rkisp1/rkisp1.cpp
@@ -27,6 +27,7 @@
 
 #include "algorithms/agc.h"
 #include "algorithms/algorithm.h"
+#include "algorithms/blc.h"
 #include "algorithms/sdg.h"
 #include "libipa/camera_sensor_helper.h"
 
@@ -126,6 +127,7 @@ int IPARkISP1::init(const IPASettings &settings, unsigned int hwRevision)
 
 	/* Construct our Algorithms */
 	algorithms_.push_back(std::make_unique<algorithms::Agc>());
+	algorithms_.push_back(std::make_unique<algorithms::BlackLevelCorrection>());
 	algorithms_.push_back(std::make_unique<algorithms::SensorDeGamma>());
 
 	return 0;
-- 
2.32.0