[libcamera-devel] [PATCH v2 1/5] libcamera: Add Transform enum to represet 2d plane transforms.

[David Plowman]

We implement 2d transforms as an enum class with 8 elements,
consisting of the usual 2d plane transformations (flips, rotations
etc.).

The transform is made up of 3 bits, indicating whether the transform
includes: a transpose, a horizontal flip (mirror) and a vertical flip.
---
 include/libcamera/meson.build |  1 +
 include/libcamera/transform.h | 58 ++++++++++++++++++++++++
 src/libcamera/meson.build     |  1 +
 src/libcamera/transform.cpp   | 83 +++++++++++++++++++++++++++++++++++
 4 files changed, 143 insertions(+)
 create mode 100644 include/libcamera/transform.h
 create mode 100644 src/libcamera/transform.cpp

diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
index cdb8e03..7fae5e5 100644
--- a/include/libcamera/meson.build
+++ b/include/libcamera/meson.build
@@ -19,6 +19,7 @@ libcamera_public_headers = files([
     'span.h',
     'stream.h',
     'timer.h',
+    'transform.h',
 ])
 
 include_dir = join_paths(libcamera_include_dir, 'libcamera')
diff --git a/include/libcamera/transform.h b/include/libcamera/transform.h
new file mode 100644
index 0000000..658beb9
--- /dev/null
+++ b/include/libcamera/transform.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Raspberry Pi (Trading) Limited
+ *
+ * transform.h - Implementation of 2d plane transforms
+ */
+
+#ifndef __LIBCAMERA_TRANSFORM_H__
+#define __LIBCAMERA_TRANSFORM_H__
+
+#include <string>
+
+namespace libcamera {
+
+enum class Transform : int {
+	Identity = 0,
+	Rot0 = Identity,
+	HFlip = 1,
+	VFlip = 2,
+	HVFlip = HFlip | VFlip,
+	Rot180 = HVFlip,
+	Transpose = 4,
+	Rot270 = HFlip | Transpose,
+	Rot90 = VFlip | Transpose,
+	Rot180Transpose = HFlip | VFlip | Transpose
+};
+
+constexpr Transform operator&(Transform t0, Transform t1)
+{
+	return static_cast<Transform>(static_cast<int>(t0) & static_cast<int>(t1));
+}
+
+constexpr Transform operator|(Transform t0, Transform t1)
+{
+	return static_cast<Transform>(static_cast<int>(t0) | static_cast<int>(t1));
+}
+
+constexpr Transform operator^(Transform t0, Transform t1)
+{
+	return static_cast<Transform>(static_cast<int>(t0) ^ static_cast<int>(t1));
+}
+
+Transform operator*(Transform t0, Transform t1);
+
+Transform operator-(Transform t);
+
+constexpr bool operator!(Transform t)
+{
+	return t == Transform::Identity;
+}
+
+Transform transformFromRotation(int angle, bool *success = nullptr);
+
+std::string transformToString(Transform t);
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_TRANSFORM_H__ */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index bada45b..b46247d 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -44,6 +44,7 @@ libcamera_sources = files([
     'sysfs.cpp',
     'thread.cpp',
     'timer.cpp',
+    'transform.cpp',
     'utils.cpp',
     'v4l2_controls.cpp',
     'v4l2_device.cpp',
diff --git a/src/libcamera/transform.cpp b/src/libcamera/transform.cpp
new file mode 100644
index 0000000..5f00a5c
--- /dev/null
+++ b/src/libcamera/transform.cpp
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Raspberry Pi (Trading) Limited
+ *
+ * transform.cpp - implementation of 2d plane transforms.
+ */
+
+#include <libcamera/transform.h>
+
+/**
+ * \file transform.h
+ * \brief Enum to represent a 2d plane transforms.
+ */
+
+namespace libcamera {
+
+Transform operator*(Transform t0, Transform t1)
+{
+	/*
+	 * Reorder the operations so that we imagine doing t1's transpose
+	 * (if any) after t0's flips. The effect is to swap t0's hflips for
+	 * vflips and vice versa, after which we can just xor all the bits.
+	 */
+	Transform reordered = t0;
+	if (!!(t1 & Transform::Transpose))
+		reordered = (t0 & Transform::Transpose) |
+			    (!!(t0 & Transform::HFlip) ? Transform::VFlip : Transform::Identity) |
+			    (!!(t0 & Transform::VFlip) ? Transform::HFlip : Transform::Identity);
+
+	return reordered ^ t1;
+}
+
+Transform operator-(Transform t)
+{
+	/* All are self-inverses, except for Rot270 and Rot90. */
+	static const Transform inverses[] = {
+		Transform::Identity, Transform::HFlip, Transform::VFlip, Transform::HVFlip,
+		Transform::Transpose, Transform::Rot90, Transform::Rot270, Transform::Rot180Transpose
+	};
+
+	return inverses[static_cast<int>(t)];
+}
+
+Transform transformFromRotation(int angle, bool *success)
+{
+	angle = angle % 360;
+	if (angle < 0)
+		angle += 360;
+
+	if (success != nullptr)
+		*success = true;
+
+	if (angle == 0)
+		return Transform::Identity;
+	else if (angle == 90)
+		return Transform::Rot90;
+	else if (angle == 180)
+		return Transform::Rot180;
+	else if (angle == 270)
+		return Transform::Rot270;
+	else if (success != nullptr)
+		*success = false;
+
+	return Transform::Identity;
+}
+
+std::string transformToString(Transform t)
+{
+	static const char *strings[] = {
+		"identity",
+		"hflip",
+		"vflip",
+		"hvflip",
+		"transpose",
+		"rot270",
+		"rot90",
+		"rot180transpose"
+	};
+
+	return strings[static_cast<int>(t)];
+}
+
+} /* namespace libcamera */
-- 
2.20.1