Operator Reference
polar_trans_region (Operator)
polar_trans_region — Transform a region within an annular arc to polar coordinates.
Signature
polar_trans_region(Region : PolarTransRegion : Row, Column, AngleStart, AngleEnd, RadiusStart, RadiusEnd, Width, Height, Interpolation : )
Description
polar_trans_region transforms a Region within the
annular arc specified by the center point (Row,
Column), the radii RadiusStart and
RadiusEnd and the angles AngleStart and
AngleEnd to its polar coordinate version in a virtual image
of the dimensions Width x Height.
The polar transformation is a change of the coordinate
system. Instead of a row and a column coordinate, each point's
position is expressed by its radius r (i.e. the distance to the
center point Row, Column) and the angle phi
between the column axis (through the center point) and the line from
the center point towards the point. Note that this transformation is
not affine.
The coordinate (0,0) in the output region always corresponds to
the point in the input region that is specified by
RadiusStart and AngleStart. Analogously, the
coordinate (Height-1, Width-1) corresponds to
the point in the input region 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 region. By suitably exchanging the values of these
parameters (e.g., AngleStart > AngleEnd or
RadiusStart > RadiusEnd), any desired
orientation of the output region can be achieved.
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
Height-1, calculation will be sped up through an
optimized routine.
The radii and angles are inclusive, which means that the first row
of the virtual 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
(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 parameter Interpolation is used to select the
interpolation method 'bilinear' or
'nearest_neighbor'. Setting Interpolation to
'bilinear' leads to smoother region boundaries, especially
if regions are enlarged. However, the runtime increases
significantly.
If more than one region is passed in Region, their polar
transformations are computed individually and stored as a tuple in
PolarTransRegion. Please note that the indices of an
input region and its transformation only correspond if the system
variable 'store_empty_regions' is set to 'true'
(see set_system). Otherwise empty output regions are
discarded and the length of the input tuple Region is most
likely not equal to the length of the output tuple
PolarTransRegion.
Further Information
For an explanation of the different 2D coordinate systems used in HALCON, see the introduction of chapter Transformations / 2D Transformations.
Attention
If Width or Height are chosen greater than the
dimensions of the current image, the system variable
'clip_region' should be set to 'false' (see
set_system). Otherwise, an output region that does not lie
within the dimensions of the current image can produce an error
message.
Execution Information
- 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 internal data level.
Parameters
Region (input_object) region(-array) → object
Input region.
PolarTransRegion (output_object) region(-array) → object
Output region.
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 column coordinate
0 of PolarTransRegion.
Default: 0.0
Suggested values: 0.0, 0.78539816, 1.57079632, 3.141592654, 6.2831853, 12.566370616
Value range:
-6.2831853
≤
AngleStart
≤
6.2831853
AngleEnd (input_control) angle.rad → (real)
Angle of the ray to be mapped to column coordinate
Width-1 of PolarTransRegion.
Default: 6.2831853
Suggested values: 0.0, 0.78539816, 1.57079632, 3.141592654, 6.2831853, 12.566370616
Value range:
-6.2831853
≤
AngleEnd
≤
6.2831853
RadiusStart (input_control) number → (real / integer)
Radius of the circle to be mapped to row coordinate
0 of PolarTransRegion.
Default: 0
Suggested values: 0, 16, 32, 64, 100, 128, 256, 512
Value range:
0
≤
RadiusStart
≤
32767
RadiusEnd (input_control) number → (real / integer)
Radius of the circle to be mapped to row coordinate
Height-1 of PolarTransRegion.
Default: 100
Suggested values: 0, 16, 32, 64, 100, 128, 256, 512
Value range:
0
≤
RadiusEnd
≤
32767
Width (input_control) extent.x → (integer)
Width of the virtual output image.
Default: 512
Suggested values: 256, 320, 512, 640, 800, 1024
Value range:
2
≤
Width
≤
32767
Height (input_control) extent.y → (integer)
Height of the virtual output image.
Default: 512
Suggested values: 240, 256, 480, 512, 600, 1024
Value range:
2
≤
Height
≤
32767
Interpolation (input_control) string → (string)
Interpolation method for the transformation.
Default: 'nearest_neighbor'
List of values: 'bilinear', 'nearest_neighbor'
See also
polar_trans_image_ext,
polar_trans_image_inv,
polar_trans_region_inv,
polar_trans_contour_xld,
polar_trans_contour_xld_inv
Module
Foundation