Apply an arbitrary affine transformation to XLD polygons.

affine_trans_polygon_xld applies an arbitrary affine transformation, i.e., scaling, rotation, translation, and slant (skewing), to the XLD polygons given in Polygons and returns the transformed polygons in PolygonsAffinTrans. The affine transformation is described by the homogeneous transformation matrix given in HomMat2D. This matrix 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 XLD contours that are possibly referenced by Polygons are neither transformed nor stored with the output polygons, since this is generally impossible without creating inconsistencies for the attributes of the XLD contours. Hence, operators that access the contours associated with a polygon, e.g., split_contours_xld will not work correctly.

affine_trans_polygon_xld returns 2 (H_MSG_TRUE) if all parameter values are correct. If necessary, an exception is raised.

affine_trans_polygon_xld is reentrant and automatically parallelized (on tuple level).

hom_mat2d_identity, hom_mat2d_translate, hom_mat2d_rotate, hom_mat2d_scale

affine_trans_image, affine_trans_region, affine_trans_contour_xld

Sub-pixel operators