Message ID | 20200821155641.11839-2-david.plowman@raspberrypi.com |
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State | Superseded |
Headers | show |
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Related | show |
Hi David, Thank you for the patch. s/represet/represent/ in the subject line. On Fri, Aug 21, 2020 at 04:56:37PM +0100, David Plowman wrote: > 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. > > Signed-off-by: David Plowman <david.plowman@raspberrypi.com> > --- > include/libcamera/meson.build | 1 + > include/libcamera/transform.h | 73 +++++++++ > src/libcamera/meson.build | 1 + > src/libcamera/transform.cpp | 301 ++++++++++++++++++++++++++++++++++ > 4 files changed, 376 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..7d88937 > --- /dev/null > +++ b/include/libcamera/transform.h > @@ -0,0 +1,73 @@ > +/* SPDX-License-Identifier: LGPL-2.1-or-later */ > +/* > + * Copyright (C) 2020, Raspberry Pi (Trading) Limited > + * > + * transform.h - 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)); > +} > + > +constexpr Transform &operator&=(Transform &t0, Transform t1) > +{ > + return t0 = t0 & t1; > +} > + > +constexpr Transform &operator|=(Transform &t0, Transform t1) > +{ > + return t0 = t0 | t1; > +} > + > +constexpr Transform &operator^=(Transform &t0, Transform t1) > +{ > + return t0 = t0 ^ 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); > + > +const char *transformToString(Transform t); > + > +} /* namespace libcamera */ > + > +#endif /* __LIBCAMERA_TRANSFORM_H__ */ > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build > index af2f3d9..edec55e 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..2944efc > --- /dev/null > +++ b/src/libcamera/transform.cpp > @@ -0,0 +1,301 @@ > +/* SPDX-License-Identifier: LGPL-2.1-or-later */ > +/* > + * Copyright (C) 2020, Raspberry Pi (Trading) Limited > + * > + * transform.cpp - 2D plane transforms. Nitpicking, no need for a period at the end here, or at the end of \brief and \param statements below. > + */ > + > +#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. I'm now used to this, but a reader may not find this "usual". How about linking to an external resource, such as https://en.wikipedia.org/wiki/Dihedral_group_of_order_8#The_symmetry_group_of_a_square:_dihedral_group_of_order_8 ? Maybe at the end of this documentation block with a \sa tag ? But that resource may be confusing though, as it defines the symmetry group based on a combination of Identity, Rot90 and HFlip operations, while we use a binary encoding where bits correspond to HFlip, VFlip and Transpose. > Each of these transforms can be constructed > + * out of 3 atomic 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 > + * atomic operations: > + * > + * bit 0 - presence of a horizontal flip\n > + * bit 1 - presence of a vertical flip\n > + * bit 2 - presence of a transposition. Maybe this should be a list ? * - bit 0 - presence of a horizontal flip * - bit 1 - presence of a vertical flip * - bit 2 - presence of a transposition > + * > + * We regard these 3 atomic 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 > +~~~ For a minute I've wondered if we could render something more visual, such as +----- | -----+----+ +--- | | | | | (for a 90° rotation), but I think it's too much hassle for now. We may convert some diagrams to SVG in the documentation in the future, in which case we'll improve this, but for now I think it's OK as-is (unless you believe it would be good to change the ascii-art representation already). > + * 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). > + */ > + > +/** > + * \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. t1 is applied first, then t0. You can use \a t1 and \a t0 to refer to the parameters, it will highlight them. > + * \param[in] t0 The first transform. > + * \param[in] t1 The second transform. t1 is apply first, then t0, yet t0 is the first and t1 the second transform. How about * \brief Compose two transforms together. t0 is applied first, then t1. * \param[in] t1 The second transform * \param[in] t0 The first transform *... */ Transform operator*(Transform t1, Transform t0) > + * > + * For example, `Transpose * HFlip` performs `HFlip` first and then the > + * `Transpose` yielding `Rot270`, as shown below. I'd move the second sentence from the brief here: * Composing transforms follows the mathematical function composition notation. * When performing t1 * t0, \a t0 is applied first, 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 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)) { It would be nice to have a bool conversion function to be able to write if (t1 & Transform::Transpose) { If we turn the enum into a class one day... :-) With these small issues addressed, Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > + reordered = t0 & Transform::Transpose; > + if (!!(t0 & Transform::HFlip)) > + reordered |= Transform::VFlip; > + if (!!(t0 & Transform::VFlip)) > + reordered |= Transform::HFlip; > + } > + > + return reordered ^ t1; > +} > + > +/** > + * \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. > + */ > + > +/** > + * \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 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 */
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..7d88937 --- /dev/null +++ b/include/libcamera/transform.h @@ -0,0 +1,73 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2020, Raspberry Pi (Trading) Limited + * + * transform.h - 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)); +} + +constexpr Transform &operator&=(Transform &t0, Transform t1) +{ + return t0 = t0 & t1; +} + +constexpr Transform &operator|=(Transform &t0, Transform t1) +{ + return t0 = t0 | t1; +} + +constexpr Transform &operator^=(Transform &t0, Transform t1) +{ + return t0 = t0 ^ 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); + +const char *transformToString(Transform t); + +} /* namespace libcamera */ + +#endif /* __LIBCAMERA_TRANSFORM_H__ */ diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build index af2f3d9..edec55e 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..2944efc --- /dev/null +++ b/src/libcamera/transform.cpp @@ -0,0 +1,301 @@ +/* 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 atomic 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 + * atomic operations: + * + * bit 0 - presence of a horizontal flip\n + * bit 1 - presence of a vertical flip\n + * bit 2 - presence of a transposition. + * + * We regard these 3 atomic 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). + */ + +/** + * \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. t1 is applied first, then t0. + * \param[in] t0 The first transform. + * \param[in] t1 The second transform. + * + * 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 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; + if (!!(t0 & Transform::HFlip)) + reordered |= Transform::VFlip; + if (!!(t0 & Transform::VFlip)) + reordered |= Transform::HFlip; + } + + return reordered ^ t1; +} + +/** + * \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. + */ + +/** + * \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 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 */
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. Signed-off-by: David Plowman <david.plowman@raspberrypi.com> --- include/libcamera/meson.build | 1 + include/libcamera/transform.h | 73 +++++++++ src/libcamera/meson.build | 1 + src/libcamera/transform.cpp | 301 ++++++++++++++++++++++++++++++++++ 4 files changed, 376 insertions(+) create mode 100644 include/libcamera/transform.h create mode 100644 src/libcamera/transform.cpp