| Message ID | 20230718105210.83558-7-jacopo.mondi@ideasonboard.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series |
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| Related | show |
Hi Jacopo Thanks for doing this! On Tue, 18 Jul 2023 at 11:52, Jacopo Mondi <jacopo.mondi@ideasonboard.com> wrote: > > The current definition of operator*(Transform t1, Transform t0) follows > the function composition notion, where t0 is applied first then t1 is > applied last. > > In order to introduce operator*(Orientation, Transform) where a > Transform is applied on top of an Orientation, invert the operand order > of operator*(Transform, Transform) so that usage of operator* with both > Orientation and Transform can be made associative. > > For example: > > Orientation o; > Transform t = t1 * t2 > Transform t3 = o * t Strictly, o * t gives us an orientation and not a transform. But otherwise I agree! Reviewed-by: David Plowman <david.plowman@raspberrypi.com> Thanks! David > = o * (t1 * t2) = (o * t1) * t2 = o * t1 * t2 > > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> > --- > src/libcamera/camera_sensor.cpp | 4 ++-- > src/libcamera/transform.cpp | 19 +++++++++++-------- > 2 files changed, 13 insertions(+), 10 deletions(-) > > diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp > index 3ba364c44a40..038d8b959072 100644 > --- a/src/libcamera/camera_sensor.cpp > +++ b/src/libcamera/camera_sensor.cpp > @@ -1051,7 +1051,7 @@ Transform CameraSensor::validateTransform(Transform *transform) const > * Combine the requested transform to compensate the sensor mounting > * rotation. > */ > - Transform combined = *transform * rotationTransform_; > + Transform combined = rotationTransform_ * *transform; > > /* > * We combine the platform and user transform, but must "adjust away" > @@ -1080,7 +1080,7 @@ Transform CameraSensor::validateTransform(Transform *transform) const > * If the sensor can do no transforms, then combined must be > * changed to the identity. The only user transform that gives > * rise to this is the inverse of the rotation. (Recall that > - * combined = transform * rotationTransform.) > + * combined = rotationTransform * transform.) > */ > *transform = -rotationTransform_; > combined = Transform::Identity; > diff --git a/src/libcamera/transform.cpp b/src/libcamera/transform.cpp > index c70cac3f14ee..d192d63d9290 100644 > --- a/src/libcamera/transform.cpp > +++ b/src/libcamera/transform.cpp > @@ -189,14 +189,17 @@ Input image | | goes to output image | | > */ > > /** > - * \brief Compose two transforms together > - * \param[in] t1 The second transform > - * \param[in] t0 The first transform > + * \brief Compose two transforms by applying \a t0 first then \a t1 > + * \param[in] t0 The first transform to apply > + * \param[in] t1 The second transform to apply > + * > + * Compose two transforms by applying \a t1 after \a t0. The operation > + * is conceptually equivalent to the canonical notion of function composition, > + * with inverse order of operands. If in the canonical function composition > + * notation "f * g" equals to "f(g())", the notation for Transforms composition > + * "t0 * t1" equals to "t1(t0()))" where \a t0 is applied first, then \a t1. > * > - * 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 > + * For example, `HFlip * Transpose` performs `HFlip` first and then the > * `Transpose` yielding `Rot270`, as shown below. > ~~~ > A-B B-A B-D > @@ -206,7 +209,7 @@ Input image | | -> HFLip -> | | -> Transpose -> | | = Rot270 > * 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) > +Transform operator*(Transform t0, Transform t1) > { > /* > * Reorder the operations so that we imagine doing t0's transpose > -- > 2.40.1 >
diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp index 3ba364c44a40..038d8b959072 100644 --- a/src/libcamera/camera_sensor.cpp +++ b/src/libcamera/camera_sensor.cpp @@ -1051,7 +1051,7 @@ Transform CameraSensor::validateTransform(Transform *transform) const * Combine the requested transform to compensate the sensor mounting * rotation. */ - Transform combined = *transform * rotationTransform_; + Transform combined = rotationTransform_ * *transform; /* * We combine the platform and user transform, but must "adjust away" @@ -1080,7 +1080,7 @@ Transform CameraSensor::validateTransform(Transform *transform) const * If the sensor can do no transforms, then combined must be * changed to the identity. The only user transform that gives * rise to this is the inverse of the rotation. (Recall that - * combined = transform * rotationTransform.) + * combined = rotationTransform * transform.) */ *transform = -rotationTransform_; combined = Transform::Identity; diff --git a/src/libcamera/transform.cpp b/src/libcamera/transform.cpp index c70cac3f14ee..d192d63d9290 100644 --- a/src/libcamera/transform.cpp +++ b/src/libcamera/transform.cpp @@ -189,14 +189,17 @@ Input image | | goes to output image | | */ /** - * \brief Compose two transforms together - * \param[in] t1 The second transform - * \param[in] t0 The first transform + * \brief Compose two transforms by applying \a t0 first then \a t1 + * \param[in] t0 The first transform to apply + * \param[in] t1 The second transform to apply + * + * Compose two transforms by applying \a t1 after \a t0. The operation + * is conceptually equivalent to the canonical notion of function composition, + * with inverse order of operands. If in the canonical function composition + * notation "f * g" equals to "f(g())", the notation for Transforms composition + * "t0 * t1" equals to "t1(t0()))" where \a t0 is applied first, then \a t1. * - * 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 + * For example, `HFlip * Transpose` performs `HFlip` first and then the * `Transpose` yielding `Rot270`, as shown below. ~~~ A-B B-A B-D @@ -206,7 +209,7 @@ Input image | | -> HFLip -> | | -> Transpose -> | | = Rot270 * 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) +Transform operator*(Transform t0, Transform t1) { /* * Reorder the operations so that we imagine doing t0's transpose
The current definition of operator*(Transform t1, Transform t0) follows the function composition notion, where t0 is applied first then t1 is applied last. In order to introduce operator*(Orientation, Transform) where a Transform is applied on top of an Orientation, invert the operand order of operator*(Transform, Transform) so that usage of operator* with both Orientation and Transform can be made associative. For example: Orientation o; Transform t = t1 * t2 Transform t3 = o * t = o * (t1 * t2) = (o * t1) * t2 = o * t1 * t2 Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> --- src/libcamera/camera_sensor.cpp | 4 ++-- src/libcamera/transform.cpp | 19 +++++++++++-------- 2 files changed, 13 insertions(+), 10 deletions(-)