polar_trans_image_extpolar_trans_image_extPolarTransImageExtPolarTransImageExtpolar_trans_image_ext (Operator)

Name

polar_trans_image_extpolar_trans_image_extPolarTransImageExtPolarTransImageExtpolar_trans_image_ext — Transform an annular arc in an image to polar coordinates.

Signature

Description

polar_trans_image_extpolar_trans_image_extPolarTransImageExtPolarTransImageExtpolar_trans_image_ext transforms the annular arc specified by the center point (RowRowRowrowrow, ColumnColumnColumncolumncolumn), the radii RadiusStartRadiusStartRadiusStartradiusStartradius_start and RadiusEndRadiusEndRadiusEndradiusEndradius_end and the angles AngleStartAngleStartAngleStartangleStartangle_start and AngleEndAngleEndAngleEndangleEndangle_end in the image ImageImageImageimageimage to its polar coordinate version in the image PolarTransImagePolarTransImagePolarTransImagepolarTransImagepolar_trans_image of the dimensions WidthWidthWidthwidthwidth x HeightHeightHeightheightheight.

The upper left pixel in the output image always corresponds to the point in the input image that is specified by RadiusStartRadiusStartRadiusStartradiusStartradius_start and AngleStartAngleStartAngleStartangleStartangle_start. Analogously, the lower right pixel in the output image always corresponds to the point in the input image that is specified by RadiusEndRadiusEndRadiusEndradiusEndradius_end and AngleEndAngleEndAngleEndangleEndangle_end. In the usual mode (AngleStartAngleStartAngleStartangleStartangle_start < AngleEndAngleEndAngleEndangleEndangle_end and RadiusStartRadiusStartRadiusStartradiusStartradius_start < RadiusEndRadiusEndRadiusEndradiusEndradius_end), the polar transformation is performed in the mathematically positive orientation (counterclockwise). Furthermore, points with smaller radii lie in the upper part of the output image. By suitably exchanging the values of these parameters (e.g., AngleStartAngleStartAngleStartangleStartangle_start > AngleEndAngleEndAngleEndangleEndangle_end or RadiusStartRadiusStartRadiusStartradiusStartradius_start > RadiusEndRadiusEndRadiusEndradiusEndradius_end), any desired orientation of the output image can be achieved.

The parameter InterpolationInterpolationInterpolationinterpolationinterpolation is used to select the interpolation method 'bilinear'"bilinear""bilinear""bilinear""bilinear" or 'nearest_neighbor'"nearest_neighbor""nearest_neighbor""nearest_neighbor""nearest_neighbor". With 'nearest_neighbor'"nearest_neighbor""nearest_neighbor""nearest_neighbor""nearest_neighbor", the gray value of a pixel in the output image is determined by the gray value of the closest pixel in the input image. With 'bilinear'"bilinear""bilinear""bilinear""bilinear", the gray value of a pixel in the output image is determined by bilinear interpolation of the gray values of the four closest pixels in the input image. The mode 'bilinear'"bilinear""bilinear""bilinear""bilinear" results in images of better quality, but is slower than the mode 'nearest_neighbor'"nearest_neighbor""nearest_neighbor""nearest_neighbor""nearest_neighbor".

The angles can be chosen from all real numbers. Center point and radii can be real as well. However, if they are both integers and the difference of RadiusEndRadiusEndRadiusEndradiusEndradius_end and RadiusStartRadiusStartRadiusStartradiusStartradius_start equals the height HeightHeightHeightheightheight of the destination image, calculation will be sped up through an optimized routine.

The radii and angles are inclusive, which means that the first row of the target image contains the circle with radius RadiusStartRadiusStartRadiusStartradiusStartradius_start and the last row contains the circle with radius RadiusEndRadiusEndRadiusEndradiusEndradius_end. For complete circles, where the difference between AngleStartAngleStartAngleStartangleStartangle_start and AngleEndAngleEndAngleEndangleEndangle_end equals (360 degrees), this also means that the first column of the target image will be the same as the last.

To avoid this, do not make this difference , but degrees instead.

The call polar_trans_image(Image, PolarTransImage, Row, Column, Width, Height)polar_trans_image(Image, PolarTransImage, Row, Column, Width, Height)PolarTransImage(Image, PolarTransImage, Row, Column, Width, Height)PolarTransImage(Image, PolarTransImage, Row, Column, Width, Height)polar_trans_image(Image, PolarTransImage, Row, Column, Width, Height) produces the same result as the call polar_trans_image_ext(Image, PolarTransImage, Row-0.5, Column-0.5, 6.2831853, 6.2831853/Width, 0, Height-1, Width, Height, 'nearest_neighbor')polar_trans_image_ext(Image, PolarTransImage, Row-0.5, Column-0.5, 6.2831853, 6.2831853/Width, 0, Height-1, Width, Height, "nearest_neighbor")PolarTransImageExt(Image, PolarTransImage, Row-0.5, Column-0.5, 6.2831853, 6.2831853/Width, 0, Height-1, Width, Height, "nearest_neighbor")PolarTransImageExt(Image, PolarTransImage, Row-0.5, Column-0.5, 6.2831853, 6.2831853/Width, 0, Height-1, Width, Height, "nearest_neighbor")polar_trans_image_ext(Image, PolarTransImage, Row-0.5, Column-0.5, 6.2831853, 6.2831853/Width, 0, Height-1, Width, Height, "nearest_neighbor").

The offset of 0.5 is necessary since polar_trans_imagepolar_trans_imagePolarTransImagePolarTransImagepolar_trans_image does not do exact nearest neighbor interpolation and the radii and angles can be calculated using the information in the above paragraph and knowing that polar_trans_imagepolar_trans_imagePolarTransImagePolarTransImagepolar_trans_image does not handle its arguments inclusively. The start angle is bigger than the end angle to make polar_trans_image_extpolar_trans_image_extPolarTransImageExtPolarTransImageExtpolar_trans_image_ext go clockwise, just like polar_trans_imagepolar_trans_imagePolarTransImagePolarTransImagepolar_trans_image does.

polar_trans_image_extpolar_trans_image_extPolarTransImageExtPolarTransImageExtpolar_trans_image_ext can be executed on an OpenCL device if the input image does not exceed the maximum size of image objects of the selected device. Due to numerical reasons, there can be slight differences in the output compared to the execution on the CPU.

Additionally, for images of type 'byte'"byte""byte""byte""byte", 'int2'"int2""int2""int2""int2" or 'uint2'"uint2""uint2""uint2""uint2" the system parameter 'int_zooming'"int_zooming""int_zooming""int_zooming""int_zooming" selects between fast calculation in fixed point arithmetics ('int_zooming'"int_zooming""int_zooming""int_zooming""int_zooming" = 'true'"true""true""true""true") and highly accurate calculation in floating point arithmetics ('int_zooming'"int_zooming""int_zooming""int_zooming""int_zooming" = 'false'"false""false""false""false"). Fixed point calculation can lead to minor gray value deviations and pixels with undefined gray values.

Further Information

For an explanation of the different 2D coordinate systems used in HALCON, see the introduction of chapter Transformations / 2D Transformations.

Attention

For speed reasons, the domain of the input image is ignored. The output image always has a complete rectangle as its domain.

Execution Information

• 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

See also

polar_trans_image_invpolar_trans_image_invPolarTransImageInvPolarTransImageInvpolar_trans_image_inv, polar_trans_regionpolar_trans_regionPolarTransRegionPolarTransRegionpolar_trans_region, polar_trans_region_invpolar_trans_region_invPolarTransRegionInvPolarTransRegionInvpolar_trans_region_inv, polar_trans_contour_xldpolar_trans_contour_xldPolarTransContourXldPolarTransContourXldpolar_trans_contour_xld, polar_trans_contour_xld_invpolar_trans_contour_xld_invPolarTransContourXldInvPolarTransContourXldInvpolar_trans_contour_xld_inv

Module

Foundation