projective_trans_imageT_projective_trans_imageProjectiveTransImageProjectiveTransImageprojective_trans_image (算子)

名称

projective_trans_imageT_projective_trans_imageProjectiveTransImageProjectiveTransImageprojective_trans_image — 对图像应用投影变换。

签名

描述

projective_trans_imageprojective_trans_imageProjectiveTransImageProjectiveTransImageProjectiveTransImageprojective_trans_image applies the projective transformation (homography) determined by the homogeneous transformation matrix HomMat2DHomMat2DHomMat2DHomMat2DhomMat2Dhom_mat_2d on the input image ImageImageImageImageimageimage and stores the result into the output image TransImageTransImageTransImageTransImagetransImagetrans_image。

If the parameter AdaptImageSizeAdaptImageSizeAdaptImageSizeAdaptImageSizeadaptImageSizeadapt_image_size is set to 'false'"false""false""false""false""false", TransImageTransImageTransImageTransImagetransImagetrans_image will have the same size as ImageImageImageImageimageimage; if AdaptImageSizeAdaptImageSizeAdaptImageSizeAdaptImageSizeadaptImageSizeadapt_image_size is 'true'"true""true""true""true""true", the output image size will be automatically adapted so that all non-negative points of the transformed image are visible.

The parameter InterpolationInterpolationInterpolationInterpolationinterpolationinterpolation determines, which interpolation method is used to determine the gray values of the output image. For InterpolationInterpolationInterpolationInterpolationinterpolationinterpolation = 'nearest_neighbor'"nearest_neighbor""nearest_neighbor""nearest_neighbor""nearest_neighbor""nearest_neighbor", the gray value is determined from the nearest pixel in the input image. This mode is very fast, but also leads to the typical “jagged” appearance for large enlargements of the image. For InterpolationInterpolationInterpolationInterpolationinterpolationinterpolation = 'bilinear'"bilinear""bilinear""bilinear""bilinear""bilinear", the gray values are interpolated bilinearly, leading to longer runtimes, but also to significantly improved results.

The parameter TransformDomainTransformDomainTransformDomainTransformDomaintransformDomaintransform_domain can be used to determine whether the domain of ImageImageImageImageimageimage is also transformed. Since the transformation of the domain costs runtime, this parameter should be used to specify whether this is desired or not. If TransformDomainTransformDomainTransformDomainTransformDomaintransformDomaintransform_domain is set to 'false'"false""false""false""false""false" the domain of the input image is ignored and the complete image is transformed.

The projective transformation matrix could for example be created using the operator vector_to_proj_hom_mat2dvector_to_proj_hom_mat2dVectorToProjHomMat2dVectorToProjHomMat2dVectorToProjHomMat2dvector_to_proj_hom_mat2d。

In a homography the points to be projected are represented by homogeneous vectors of the form (x,y,w). A Euclidean point can be derived as (x',y') = 。

Just like in affine_trans_imageaffine_trans_imageAffineTransImageAffineTransImageAffineTransImageaffine_trans_image, x represents the row coordinate while y represents the column coordinate in projective_trans_imageprojective_trans_imageProjectiveTransImageProjectiveTransImageProjectiveTransImageprojective_trans_image. With this convention, affine transformations are a special case of projective transformations in which the last row of HomMat2DHomMat2DHomMat2DHomMat2DhomMat2Dhom_mat_2d is of the form (0,0,c).

For images of type 'byte'"byte""byte""byte""byte""byte" or 'uint2'"uint2""uint2""uint2""uint2""uint2" the system parameter 'int_zooming'"int_zooming""int_zooming""int_zooming""int_zooming""int_zooming" selects between fast calculation in floating point arithmetics ('int_zooming'"int_zooming""int_zooming""int_zooming""int_zooming""int_zooming" = 'true'"true""true""true""true""true") and highly accurate floating point arithmetics ('int_zooming'"int_zooming""int_zooming""int_zooming""int_zooming""int_zooming" = 'false'"false""false""false""false""false"). Especially for InterpolationInterpolationInterpolationInterpolationinterpolationinterpolation = 'bilinear'"bilinear""bilinear""bilinear""bilinear""bilinear", however, the faster calculation can lead to minor gray value deviations since the faster algorithm is less accurate and only has an accuracy around times the size of the image. Therefore, when applying large scales 'int_zooming'"int_zooming""int_zooming""int_zooming""int_zooming""int_zooming" = 'false'"false""false""false""false""false" is recommended.

注意

The used coordinate system is the same as in affine_trans_pixelaffine_trans_pixelAffineTransPixelAffineTransPixelAffineTransPixelaffine_trans_pixel。This means that in fact not HomMat2DHomMat2DHomMat2DHomMat2DhomMat2Dhom_mat_2d is applied but a modified version. Therefore, applying projective_trans_imageprojective_trans_imageProjectiveTransImageProjectiveTransImageProjectiveTransImageprojective_trans_image corresponds to the following chain of transformations, which is applied to each point of the image (input and output pixels as homogeneous vectors):

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_grayAreaCenterGrayAreaCenterGrayAreaCenterGrayarea_center_gray。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_rotateHomMat2dRotateHomMat2dRotateHomMat2dRotatehom_mat2d_rotate, 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 HomMat2DHomMat2DHomMat2DHomMat2DhomMat2Dhom_mat_2d before using it in projective_trans_imageprojective_trans_imageProjectiveTransImageProjectiveTransImageProjectiveTransImageprojective_trans_image：

有关 HALCON 中使用的不同二维坐标系的说明，请参阅 变换 / 二维变换 一章的引言。

projective_trans_imageprojective_trans_imageProjectiveTransImageProjectiveTransImageProjectiveTransImageprojective_trans_image 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 TransformDomainTransformDomainTransformDomainTransformDomaintransformDomaintransform_domain is set to 'false'"false""false""false""false""false". The result can diverge slightly from that calculated on the CPU.

执行信息

• 支持 OpenCL 计算设备。
• 多线程类型：可重入（与非独占算子并行运行）。
• 多线程作用域：全局（可从任何线程调用）。
• 在元组级别上自动并行化。
• 在通道级别上自动并行化。
• 在内部数据级别上自动并行化。

参数

可能的前趋

vector_to_proj_hom_mat2dvector_to_proj_hom_mat2dVectorToProjHomMat2dVectorToProjHomMat2dVectorToProjHomMat2dvector_to_proj_hom_mat2d, hom_vector_to_proj_hom_mat2dhom_vector_to_proj_hom_mat2dHomVectorToProjHomMat2dHomVectorToProjHomMat2dHomVectorToProjHomMat2dhom_vector_to_proj_hom_mat2d, proj_match_points_ransacproj_match_points_ransacProjMatchPointsRansacProjMatchPointsRansacProjMatchPointsRansacproj_match_points_ransac, proj_match_points_ransac_guidedproj_match_points_ransac_guidedProjMatchPointsRansacGuidedProjMatchPointsRansacGuidedProjMatchPointsRansacGuidedproj_match_points_ransac_guided, hom_mat3d_projecthom_mat3d_projectHomMat3dProjectHomMat3dProjectHomMat3dProjecthom_mat3d_project

另见

projective_trans_image_sizeprojective_trans_image_sizeProjectiveTransImageSizeProjectiveTransImageSizeProjectiveTransImageSizeprojective_trans_image_size, projective_trans_contour_xldprojective_trans_contour_xldProjectiveTransContourXldProjectiveTransContourXldProjectiveTransContourXldprojective_trans_contour_xld, projective_trans_regionprojective_trans_regionProjectiveTransRegionProjectiveTransRegionProjectiveTransRegionprojective_trans_region, projective_trans_point_2dprojective_trans_point_2dProjectiveTransPoint2dProjectiveTransPoint2dProjectiveTransPoint2dprojective_trans_point_2d, projective_trans_pixelprojective_trans_pixelProjectiveTransPixelProjectiveTransPixelProjectiveTransPixelprojective_trans_pixel

模块

基础

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