[libcamera-devel] [RFC PATCH 1/3] libcamera: Add ColorSpace class

[David Plowman]

This class represents a colour space by defining its YCbCr encoding,
the transfer (gamma) function is uses, and whether the output is full
or limited range.
---
 include/libcamera/color_space.h | 94 +++++++++++++++++++++++++++++++++
 include/libcamera/meson.build   |  1 +
 src/libcamera/color_space.cpp   | 43 +++++++++++++++
 src/libcamera/meson.build       |  1 +
 4 files changed, 139 insertions(+)
 create mode 100644 include/libcamera/color_space.h
 create mode 100644 src/libcamera/color_space.cpp

diff --git a/include/libcamera/color_space.h b/include/libcamera/color_space.h
new file mode 100644
index 00000000..3d990f99
--- /dev/null
+++ b/include/libcamera/color_space.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Raspberry Pi (Trading) Limited
+ *
+ * color_space.h - color space definitions
+ */
+
+#ifndef __LIBCAMERA_COLOR_SPACE_H__
+#define __LIBCAMERA_COLOR_SPACE_H__
+
+#include <string>
+
+namespace libcamera {
+
+class ColorSpace
+{
+public:
+	enum class Encoding : int {
+		UNDEFINED,
+		RAW,
+		REC601,
+		REC709,
+		REC2020,
+		VIDEO,
+	};
+
+	enum class TransferFunction : int {
+		UNDEFINED,
+		IDENTITY,
+		SRGB,
+		REC709,
+	};
+
+	enum class Range : int {
+		UNDEFINED,
+		FULL,
+		LIMITED,
+	};
+
+	constexpr ColorSpace(Encoding e, TransferFunction t, Range r)
+		: encoding(e), transferFunction(t), range(r)
+	{
+	}
+
+	constexpr ColorSpace()
+		: ColorSpace(Encoding::UNDEFINED, TransferFunction::UNDEFINED, Range::UNDEFINED)
+	{
+	}
+
+	static const ColorSpace UNDEFINED;
+	static const ColorSpace RAW;
+	static const ColorSpace JFIF;
+	static const ColorSpace SMPTE170M;
+	static const ColorSpace REC709;
+	static const ColorSpace REC2020;
+	static const ColorSpace VIDEO;
+
+	Encoding encoding;
+	TransferFunction transferFunction;
+	Range range;
+
+	bool isFullyDefined() const
+	{
+		return encoding != Encoding::UNDEFINED &&
+		       transferFunction != TransferFunction::UNDEFINED &&
+		       range != Range::UNDEFINED;
+	}
+
+	const std::string toString() const;
+};
+
+constexpr ColorSpace ColorSpace::UNDEFINED = { Encoding::UNDEFINED, TransferFunction::UNDEFINED, Range::UNDEFINED };
+constexpr ColorSpace ColorSpace::RAW = { Encoding::RAW, TransferFunction::IDENTITY, Range::FULL };
+constexpr ColorSpace ColorSpace::JFIF = { Encoding::REC601, TransferFunction::SRGB, Range::FULL };
+constexpr ColorSpace ColorSpace::SMPTE170M = { Encoding::REC601, TransferFunction::REC709, Range::LIMITED };
+constexpr ColorSpace ColorSpace::REC709 = { Encoding::REC709, TransferFunction::REC709, Range::LIMITED };
+constexpr ColorSpace ColorSpace::REC2020 = { Encoding::REC2020, TransferFunction::REC709, Range::LIMITED };
+constexpr ColorSpace ColorSpace::VIDEO = { Encoding::VIDEO, TransferFunction::REC709, Range::LIMITED };
+
+static inline bool operator==(const ColorSpace &lhs, const ColorSpace &rhs)
+{
+	return lhs.encoding == rhs.encoding &&
+	       lhs.transferFunction == rhs.transferFunction &&
+	       lhs.range == rhs.range;
+}
+
+static inline bool operator!=(const ColorSpace &lhs, const ColorSpace &rhs)
+{
+	return !(lhs == rhs);
+}
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_COLOR_SPACE_H__ */
diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
index 086c958b..7d61d285 100644
--- a/include/libcamera/meson.build
+++ b/include/libcamera/meson.build
@@ -6,6 +6,7 @@ libcamera_public_headers = files([
     'camera.h',
     'camera_manager.h',
     'class.h',
+    'color_space.h',
     'compiler.h',
     'controls.h',
     'file_descriptor.h',
diff --git a/src/libcamera/color_space.cpp b/src/libcamera/color_space.cpp
new file mode 100644
index 00000000..888762ae
--- /dev/null
+++ b/src/libcamera/color_space.cpp
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Raspberry Pi (Trading) Limited
+ *
+ * color_space.cpp - color spaces.
+ */
+
+#include <libcamera/color_space.h>
+
+/**
+ * \file color_space.h
+ * \brief Class and enums to represent colour spaces.
+ */
+
+namespace libcamera {
+
+const std::string ColorSpace::toString() const
+{
+	static const char *encodings[] = {
+		"UNDEFINED",
+		"RAW",
+		"REC601",
+		"REC709",
+		"REC2020",
+	};
+	static const char *transferFunctions[] = {
+		"UNDEFINED",
+		"IDENTITY",
+		"SRGB",
+		"REC709",
+	};
+	static const char *ranges[] = {
+		"UNDEFINED",
+		"FULL",
+		"LIMITED",
+	};
+
+	return std::string(encodings[static_cast<int>(encoding)]) + "+" +
+	       std::string(transferFunctions[static_cast<int>(transferFunction)]) + "+" +
+	       std::string(ranges[static_cast<int>(range)]);
+}
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 7e19a177..f7b48a32 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -11,6 +11,7 @@ libcamera_sources = files([
     'camera_sensor.cpp',
     'camera_sensor_properties.cpp',
     'class.cpp',
+    'color_space.cpp',
     'controls.cpp',
     'control_serializer.cpp',
     'control_validator.cpp',
-- 
2.20.1