polar_trans_image_ext🔗
Short description🔗
polar_trans_image_ext — Transform an annular arc in an image to polar coordinates.
Signature🔗
polar_trans_image_ext( image Image, out image PolarTransImage, number Row, number Column, angle.rad AngleStart, angle.rad AngleEnd, number RadiusStart, number RadiusEnd, extent.x Width, extent.y Height, string Interpolation )
Description🔗
polar_trans_image_ext transforms the annular arc specified
by the center point (Row, Column), the radii
RadiusStart and RadiusEnd and the angles
AngleStart and AngleEnd in the image
Image to its polar coordinate version in the image
PolarTransImage of the dimensions Width
x Height.
The upper left pixel in the output image always corresponds to the
point in the input image that is specified by RadiusStart
and AngleStart. Analogously, the lower right pixel in the
output image always corresponds to the point in the input image that
is specified by RadiusEnd and AngleEnd. In the
usual mode (AngleStart \(<\) AngleEnd and
RadiusStart \(<\) RadiusEnd), 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., AngleStart
\(>\) AngleEnd or RadiusStart \(>\)
RadiusEnd), any desired orientation of the output image can
be achieved.
The parameter Interpolation is used to select the
interpolation method 'bilinear' or
'nearest_neighbor'. With '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', 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' results in images of better quality, but is
slower than the mode '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 RadiusEnd and RadiusStart equals
the height Height 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
RadiusStart and the last row contains the circle with
radius RadiusEnd. For complete circles, where the
difference between AngleStart and AngleEnd equals
\(2 \pi\) (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 \(2 \pi\), but \(2 \pi (1 - \frac{1}{\textrm{Width}})\) degrees instead.
The call
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').
The offset of 0.5 is necessary since polar_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_image does not handle its arguments
inclusively. The start angle is bigger than the end angle to make
polar_trans_image_ext go clockwise, just like
polar_trans_image does.
polar_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, int2 or uint2 the system parameter 'int_zooming' selects between fast calculation in fixed point arithmetics ('int_zooming' = 'true') and highly accurate calculation in floating point arithmetics ('int_zooming' = '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🔗
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🔗
Image (input_object) (multichannel-)image(-array) → object (byte* / int2* / uint2* / real*) *allowed for compute devices
Input image.
PolarTransImage (output_object) (multichannel-)image(-array) → object (byte / int2 / uint2 / real)
Output image.
Row (input_control) number → (real / integer)
Row coordinate of the center of the arc.
Default: 256
Suggested values: 0, 16, 32, 64, 128, 240, 256, 480, 512
Column (input_control) number → (real / integer)
Column coordinate of the center of the arc.
Default: 256
Suggested values: 0, 16, 32, 64, 128, 256, 320, 512, 640
AngleStart (input_control) angle.rad → (real)
Angle of the ray to be mapped to the first column of the output image.
Default: 0.0
Suggested values: 0.0, 0.78539816, 1.57079632, 3.141592654, 6.2831853, 12.566370616
AngleEnd (input_control) angle.rad → (real)
Angle of the ray to be mapped to the last column of the output image.
Default: 6.2831853
Suggested values: 0.0, 0.78539816, 1.57079632, 3.141592654, 6.2831853, 12.566370616
RadiusStart (input_control) number → (real / integer)
Radius of the circle to be mapped to the first row of the output image.
Default: 0
Suggested values: 0, 16, 32, 64, 100, 128, 256, 512
Value range: 0 ≤ RadiusStart
RadiusEnd (input_control) number → (real / integer)
Radius of the circle to be mapped to the last row of the output image.
Default: 100
Suggested values: 0, 16, 32, 64, 100, 128, 256, 512
Value range: 0 ≤ RadiusEnd
Width (input_control) extent.x → (integer)
Width of the output image.
Default: 512
Suggested values: 256, 320, 512, 640, 800, 1024
Value range: 0 ≤ Width ≤ 32767
Height (input_control) extent.y → (integer)
Height of the output image.
Default: 512
Suggested values: 240, 256, 480, 512, 600, 1024
Value range: 0 ≤ Height ≤ 32767
Interpolation (input_control) string → (string)
Interpolation method for the transformation.
Default: 'nearest_neighbor'
List of values: 'bilinear', 'nearest_neighbor'
Combinations with other operators🔗
Combinations
See also
polar_trans_image_inv, polar_trans_region, polar_trans_region_inv, polar_trans_contour_xld, polar_trans_contour_xld_inv
Module🔗
Foundation