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Diffstat (limited to 'src/libcamera')
| -rw-r--r-- | src/libcamera/meson.build | 1 | ||||
| -rw-r--r-- | src/libcamera/transform.cpp | 322 |
2 files changed, 323 insertions, 0 deletions
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build index 18ea3261..1351dbba 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 00000000..f3e37f31 --- /dev/null +++ b/src/libcamera/transform.cpp @@ -0,0 +1,322 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2020, Raspberry Pi (Trading) Limited + * + * transform.cpp - 2D plane transforms. + */ + +#include <libcamera/transform.h> + +/** + * \file transform.h + * \brief Enum to represent and manipulate 2D plane transforms + */ + +namespace libcamera { + +/** + * \enum Transform + * \brief Enum to represent a 2D plane transform + * + * The Transform can take 8 distinct values, representing the usual 2D plane + * transforms listed below. Each of these transforms can be constructed + * out of 3 basic operations, namely a horizontal flip (mirror), a vertical + * flip, and a transposition (about the main diagonal). The transforms are + * encoded such that a single bit indicates the presence of each of the 3 + * basic operations: + * + * - bit 0 - presence of a horizontal flip + * - bit 1 - presence of a vertical flip + * - bit 2 - presence of a transposition. + * + * We regard these 3 basic operations as being applied in a specific order: + * first the two flip operations (actually they commute, so the order between + * them is unimportant) and finally any transpose operation. + * + * Functions are provided to manipulate directly the bits within the transform + * encoding, but there are also higher-level functions to invert and compose + * transforms. Transforms are composed according to the usual mathematical + * convention such that the right transform is applied first, and the left + * transform is applied second. + * + * Finally, we have a total of 8 distinct transformations, as follows (a + * couple of them have additional synonyms for convenience). We illustrate each + * with its nominal effect on a rectangle with vertices labelled A, B, C and D. + * + * **Identity** + * + * Identity transform. +~~~ + A-B A-B +Input image | | goes to output image | | + C-D C-D +~~~ + * Numeric value: 0 (no bits set). + * + * **Rot0** + * + * Synonym for `Identity` (zero degree rotation). + * + * **HFlip** + * + * Horizontal flip. +~~~ + A-B B-A +Input image | | goes to output image | | + C-D D-C +~~~ + * Numeric value: 1 (horizontal flip bit set only). + * + * **VFlip** + * + * Vertical flip. +~~~ + A-B C-D +Input image | | goes to output image | | + C-D A-B +~~~ + * Numeric value: 2 (vertical flip bit set only). + * + * **HVFlip** + * + * Horizontal and vertical flip (identical to a 180 degree rotation). +~~~ + A-B D-C +Input image | | goes to output image | | + C-D B-A +~~~ + * Numeric value: 3 (horizontal and vertical flip bits set). + * + * **Rot180** + * + * Synonym for `HVFlip` (180 degree rotation). + * + * **Transpose** + * + * Transpose (about the main diagonal). +~~~ + A-B A-C +Input image | | goes to output image | | + C-D B-D +~~~ + * Numeric value: 4 (transpose bit set only). + * + * **Rot270** + * + * Rotation by 270 degrees clockwise (90 degrees anticlockwise). +~~~ + A-B B-D +Input image | | goes to output image | | + C-D A-C +~~~ + * Numeric value: 5 (transpose and horizontal flip bits set). + * + * **Rot90** + * + * Rotation by 90 degrees clockwise (270 degrees anticlockwise). +~~~ + A-B C-A +Input image | | goes to output image | | + C-D D-B +~~~ + * Numeric value: 6 (transpose and vertical flip bits set). + * + * **Rot180Transpose** + * + * Rotation by 180 degrees followed by transpose (alternatively, transposition + * about the "opposite diagonal"). +~~~ + A-B D-B +Input image | | goes to output image | | + C-D C-A +~~~ + * Numeric value: 7 (all bits set). + * + * \sa https://en.wikipedia.org/wiki/Examples_of_groups#dihedral_group_of_order_8 + * + * The set of 2D plane transforms is also known as the symmetry group of a + * square, described in the link. Note that the group can be generated by + * only 2 elements (the horizontal flip and a 90 degree rotation, for + * example), however, the encoding used here makes the presence of the vertical + * flip explicit. + */ + +/** + * \fn operator &(Transform t0, Transform t1) + * \brief Apply bitwise AND operator between the bits in the two transforms + * \param[in] t0 The first transform + * \param[in] t1 The second transform + */ + +/** + * \fn operator |(Transform t0, Transform t1) + * \brief Apply bitwise OR operator between the bits in the two transforms + * \param[in] t0 The first transform + * \param[in] t1 The second transform + */ + +/** + * \fn operator ^(Transform t0, Transform t1) + * \brief Apply bitwise XOR operator between the bits in the two transforms + * \param[in] t0 The first transform + * \param[in] t1 The second transform + */ + +/** + * \fn operator &=(Transform &t0, Transform t1) + * \brief Apply bitwise AND-assignment operator between the bits in the two + * transforms + * \param[in] t0 The first transform + * \param[in] t1 The second transform + */ + +/** + * \fn operator |=(Transform &t0, Transform t1) + * \brief Apply bitwise OR-assignment operator between the bits in the two + * transforms + * \param[in] t0 The first transform + * \param[in] t1 The second transform + */ + +/** + * \fn operator ^=(Transform &t0, Transform t1) + * \brief Apply bitwise XOR-assignment operator between the bits in the two + * transforms + * \param[in] t0 The first transform + * \param[in] t1 The second transform + */ + +/** + * \brief Compose two transforms together + * \param[in] t1 The second transform + * \param[in] t0 The first transform + * + * Composing transforms follows the usual mathematical convention for + * composing functions. That is, when performing `t1 * t0`, \a t0 is applied + * first, and then \a t1. + * For example, `Transpose * HFlip` performs `HFlip` first and then the + * `Transpose` yielding `Rot270`, as shown below. +~~~ + A-B B-A B-D +Input image | | -> HFLip -> | | -> Transpose -> | | = Rot270 + C-D D-C A-C +~~~ + * Note that composition is generally non-commutative for Transforms, + * and not the same as XOR-ing the underlying bit representations. + */ +Transform operator*(Transform t1, Transform t0) +{ + /* + * Reorder the operations so that we imagine doing t0's transpose + * (if any) after t1's flips. The effect is to swap t1's hflips for + * vflips and vice versa, after which we can just xor all the bits. + */ + Transform reordered = t1; + if (!!(t0 & Transform::Transpose)) { + reordered = t1 & Transform::Transpose; + if (!!(t1 & Transform::HFlip)) + reordered |= Transform::VFlip; + if (!!(t1 & Transform::VFlip)) + reordered |= Transform::HFlip; + } + + return reordered ^ t0; +} + +/** + * \brief Invert a transform + * \param[in] t The transform to be inverted + * + * That is, we return the transform such that `t * (-t)` and `(-t) * t` both + * yield the identity transform. + */ +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)]; +} + +/** + * \fn operator!(Transform t) + * \brief Return `true` if the transform is the `Identity`, otherwise `false` + * \param[in] t The transform to be tested + */ + +/** + * \fn operator~(Transform t) + * \brief Return the transform with all the bits inverted individually + * \param[in] t The transform of which the bits will be inverted + * + * This inverts the bits that encode the transform in a bitwise manner. Note + * that this is not the proper inverse of transform \a t (for which use \a + * operator-). + */ + +/** + * \brief Return the transform representing a rotation of the given angle + * clockwise + * \param[in] angle The angle of rotation in a clockwise sense. Negative values + * can be used to represent anticlockwise rotations + * \param[out] success Set to `true` if the angle is a multiple of 90 degrees, + * otherwise `false` + * \return The transform corresponding to the rotation if \a success was set to + * `true`, otherwise the `Identity` transform + */ +Transform transformFromRotation(int angle, bool *success) +{ + angle = angle % 360; + if (angle < 0) + angle += 360; + + if (success != nullptr) + *success = true; + + switch (angle) { + case 0: + return Transform::Identity; + case 90: + return Transform::Rot90; + case 180: + return Transform::Rot180; + case 270: + return Transform::Rot270; + } + + if (success != nullptr) + *success = false; + + return Transform::Identity; +} + +/** + * \brief Return a character string describing the transform + * \param[in] t The transform to be described. + */ +const char *transformToString(Transform t) +{ + static const char *strings[] = { + "identity", + "hflip", + "vflip", + "hvflip", + "transpose", + "rot270", + "rot90", + "rot180transpose" + }; + + return strings[static_cast<int>(t)]; +} + +} /* namespace libcamera */ |