libcamera: software_isp: Add SwStatsCpu class

Add a CPU based SwStats implementation for SoftwareISP / SoftIPA use.

This implementation offers a configure function + functions to gather
statistics on a line by line basis. This allows CPU based software
debayering to call into interleave debayering and statistics gathering
on a line by line basis while the input data is still hot in the cache.

This implementation also allows specifying a window over which to gather
statistics instead of processing the whole frame.

Doxygen documentation by Dennis Bonke.

Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> # sc8280xp Lenovo x13s
Tested-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Milan Zamazal <mzamazal@redhat.com>
Co-developed-by: Andrey Konovalov <andrey.konovalov@linaro.org>
Signed-off-by: Andrey Konovalov <andrey.konovalov@linaro.org>
Co-developed-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Co-developed-by: Dennis Bonke <admin@dennisbonke.com>
Signed-off-by: Dennis Bonke <admin@dennisbonke.com>
Co-developed-by: Marttico <g.martti@gmail.com>
Signed-off-by: Marttico <g.martti@gmail.com>
Co-developed-by: Toon Langendam <t.langendam@gmail.com>
Signed-off-by: Toon Langendam <t.langendam@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/meson.build

@@ -50,3 +50,4 @@ libcamera_internal_headers = files([
 ])
 
 subdir('converter')
+subdir('software_isp')

include/libcamera/internal/software_isp/meson.build

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: CC0-1.0
+
+libcamera_internal_headers += files([
+    'swisp_stats.h',
+])

include/libcamera/internal/software_isp/swisp_stats.h

@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2023, Linaro Ltd
+ *
+ * swisp_stats.h - Statistics data format used by the software ISP and software IPA
+ */
+
+#pragma once
+
+#include <array>
+#include <stdint.h>
+
+namespace libcamera {
+
+/**
+ * \brief Struct that holds the statistics for the Software ISP
+ *
+ * The struct value types are large enough to not overflow.
+ * Should they still overflow for some reason, no check is performed and they
+ * wrap around.
+ */
+struct SwIspStats {
+	/**
+	 * \brief Holds the sum of all sampled red pixels
+	 */
+	uint64_t sumR_;
+	/**
+	 * \brief Holds the sum of all sampled green pixels
+	 */
+	uint64_t sumG_;
+	/**
+	 * \brief Holds the sum of all sampled blue pixels
+	 */
+	uint64_t sumB_;
+	/**
+	 * \brief Number of bins in the yHistogram
+	 */
+	static constexpr unsigned int kYHistogramSize = 16;
+	/**
+	 * \brief A histogram of luminance values
+	 */
+	std::array<uint32_t, kYHistogramSize> yHistogram;
+};
+
+} /* namespace libcamera */