Apply an arbitrary affine 2D transformation to regions.
affine_trans_region applies an arbitrary affine 2D transformation, i.e., scaling, rotation, translation, and slant (skewing), to the regions given in Region and returns the transformed regions in RegionAffineTrans. The affine transformation is described by the homogeneous transformation matrix given in HomMat2D, which can be created using the operators hom_mat2d_identity, hom_mat2d_scale, hom_mat2d_rotate, hom_mat2d_translate, etc., or be the result of operators like vector_angle_to_rigid.
The components of the homogeneous transformation matrix are interpreted as follows: The row coordinate of the image corresponds to the x coordinate of the matrix, while the column coordinate of the image corresponds to the y coordinate of the matrix. This is necessary to obtain a right-handed coordinate system for the image. In particular, this assures that rotations are performed in the correct direction. Note that the (x,y) order of the matrices quite naturally corresponds to the usual (row,column) order for coordinates in the image.
The parameter Interpolate determines whether the transformation is to be done by using interpolation internally. This can lead to smoother region boundaries, especially if regions are enlarged. However, the runtime increases drastically.
affine_trans_region in general is not reversible (clipping and discretization during rotation and scaling).
|
Region (input_object) |
region(-array) -> object |
| Region(s) to be rotated and scaled. | |
|
RegionAffineTrans (output_object) |
region(-array) -> object |
| Transformed output region(s). | |
| Number of elements: RegionAffineTrans == Region | |
|
HomMat2D (input_control) |
affine2d-array -> real |
| Input transformation matrix. | |
| Number of elements: 6 | |
|
Interpolate (input_control) |
string -> string |
| Should the transformation be done using interpolation? | |
| Default value: 'false' | |
| List of values: 'true', 'false' | |
affine_trans_region returns 2 (H_MSG_TRUE) if all parameters are correct. The behavior in case of empty input (no regions given) can be set via set_system('no_object_result',<Result>), the behavior in case of an empty input region via set_system('empty_region_result',<Result>), and the behavior in case of an empty result region via set_system('store_empty_region',<true/false>). If necessary, an exception handling is raised.
affine_trans_region is reentrant and automatically parallelized (on tuple level).
hom_mat2d_identity, hom_mat2d_scale, hom_mat2d_translate, hom_mat2d_invert, hom_mat2d_rotate
move_region, mirror_region, zoom_region
Region processing
