projective_trans_image_sizeT_projective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSize (Operator)

Name

projective_trans_image_sizeT_projective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSize — Apply a projective transformation to an image and specify the output image size.

Signature

Description

projective_trans_image_sizeprojective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSize applies the projective transformation (homography) determined by the homogeneous transformation matrix HomMat2DHomMat2DHomMat2DHomMat2DhomMat2D on the input image ImageImageImageImageimage and stores the result into the output image TransImageTransImageTransImageTransImagetransImage.

TransImageTransImageTransImageTransImagetransImage will be clipped at the output dimensions HeightHeightHeightHeightheightxWidthWidthWidthWidthwidth. Apart from this, projective_trans_image_sizeprojective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSize is identical to its alternative version projective_trans_imageprojective_trans_imageprojective_trans_imageProjectiveTransImageProjectiveTransImage.

Attention

The used coordinate system is the same as in affine_trans_pixelaffine_trans_pixelaffine_trans_pixelAffineTransPixelAffineTransPixel. This means that in fact not HomMat2DHomMat2DHomMat2DHomMat2DhomMat2D is applied but a modified version. Therefore, applying projective_trans_image_sizeprojective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSize corresponds to the following chain of transformations, which is applied to each point (Row_i, Col_i) of the image (input and output pixels as homogeneous vectors):

  / RowTrans_i \   / 1 0 -0.5 \              / 1 0 +0.5 \   / Row_i \
  | ColTrans_i | = | 0 1 -0.5 | * HomMat2D * | 0 1 +0.5 | * | Col_i |
  \    1       /   \ 0 0   1  /              \ 0 0   1  /   \  1    /

As an effect, you might get unexpected results when creating projective transformations based on coordinates that are derived from the image, e.g., by operators like area_center_grayarea_center_grayarea_center_grayAreaCenterGrayAreaCenterGray. For example, if you use this operator to calculate the center of gravity of a rotationally symmetric image and then rotate the image around this point using hom_mat2d_rotatehom_mat2d_rotatehom_mat2d_rotateHomMat2dRotateHomMat2dRotate, the resulting image will not lie on the original one. In such a case, you can compensate this effect by applying the following translations to HomMat2DHomMat2DHomMat2DHomMat2DhomMat2D before using it in projective_trans_image_sizeprojective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSize:

  hom_mat2d_translate(HomMat2D, 0.5, 0.5, HomMat2DTmp)
  hom_mat2d_translate_local(HomMat2DTmp, -0.5, -0.5, HomMat2DAdapted)
  projective_trans_image_size(Image, TransImage, HomMat2DAdapted,
	               'bilinear', 'Width', 'Height', 'false')

projective_trans_image_sizeprojective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSize can be executed on OpenCL devices if the input image does not exceed the maximum size of image objects of the selected device and the parameter TransformRegionTransformRegionTransformRegionTransformRegiontransformRegion is set to 'false'"false""false""false""false". The result can diverge slightly from that calculated on the CPU.

Parallelization

• Supports OpenCL compute devices.
• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Automatically parallelized on tuple level.
• Automatically parallelized on channel level.
• Automatically parallelized on internal data level.

Parameters

Possible Predecessors

vector_to_proj_hom_mat2dvector_to_proj_hom_mat2dvector_to_proj_hom_mat2dVectorToProjHomMat2dVectorToProjHomMat2d, hom_vector_to_proj_hom_mat2dhom_vector_to_proj_hom_mat2dhom_vector_to_proj_hom_mat2dHomVectorToProjHomMat2dHomVectorToProjHomMat2d, proj_match_points_ransacproj_match_points_ransacproj_match_points_ransacProjMatchPointsRansacProjMatchPointsRansac, proj_match_points_ransac_guidedproj_match_points_ransac_guidedproj_match_points_ransac_guidedProjMatchPointsRansacGuidedProjMatchPointsRansacGuided, hom_mat3d_projecthom_mat3d_projecthom_mat3d_projectHomMat3dProjectHomMat3dProject

See also

projective_trans_imageprojective_trans_imageprojective_trans_imageProjectiveTransImageProjectiveTransImage, projective_trans_contour_xldprojective_trans_contour_xldprojective_trans_contour_xldProjectiveTransContourXldProjectiveTransContourXld, projective_trans_regionprojective_trans_regionprojective_trans_regionProjectiveTransRegionProjectiveTransRegion, projective_trans_point_2dprojective_trans_point_2dprojective_trans_point_2dProjectiveTransPoint2dProjectiveTransPoint2d, projective_trans_pixelprojective_trans_pixelprojective_trans_pixelProjectiveTransPixelProjectiveTransPixel

Module

Foundation