hough_lines

Herror ::hough_lines ( Hobject RegionIn, const HTuple &AngleResolution, const HTuple &Threshold, const HTuple &AngleGap, const HTuple &DistGap, HTuple *Angle, HTuple *Dist ) HTuple HRegion::HoughLines ( const HTuple &AngleResolution, const HTuple &Threshold, const HTuple &AngleGap, const HTuple &DistGap, HTuple *Dist ) const

Detect lines in edge images with the help of the Hough transform and returns it in HNF.

The operator ::hough_lines allows the selection of linelike structures in a region, whereby it is not necessary that the individual points of a line are connected. This process is based on the Hough transform. The lines are returned in HNF, that is by the direction and length of their normal vector.

The parameter AngleResolution defines the degree of exactness concerning the determination of the angles. It amounts to 1 / AngleResolution degree. The parameter Threshold determines by how many points of the original region a line's hypothesis has to be supported at least in order to be taken over into the output. The parameters AngleGap and DistGap define a neighborhood of the points in the Hough image in order to determine the local maxima. The lines are returned in HNF.

Parameters

`RegionIn` (input_object)	region `->` Hobject: HRegion
Binary edge image in which the lines are to be detected.

`AngleResolution` (input_control)	integer `->` HTuple.long
Adjusting the resolution in the angle area.
Default value: 4
List of values: 1, 2, 4, 8

`Threshold` (input_control)	integer `->` HTuple.long
Threshold value in the Hough image.
Default value: 100
Typical range of values: `1 <= Threshold`

`AngleGap` (input_control)	integer `->` HTuple.long
Minimal distance of two maxima in the Hough image (direction: angle).
Default value: 5
Typical range of values: `0 <= AngleGap`

`DistGap` (input_control)	integer `->` HTuple.long
Minimal distance of two maxima in the Hough image (direction: distance).
Default value: 5
Typical range of values: `0 <= DistGap`

`Angle` (output_control)	hesseline.angle.rad-array `->` HTuple.double *
Angles (in radians) of the detected lines' normal vectors.
Typical range of values: `-1.5707963 <= Angle <= 3.1415927`

`Dist` (output_control)	hesseline.distance-array `->` HTuple.double *
Distance of the detected lines from the origin.
Typical range of values: `-1.5707963 <= Dist <= 3.1415927`
Number of elements: Dist == Angle

Result

The operator ::hough_lines returns the value H_MSG_TRUE if the input is not empty. The behavior in case of empty input (no input regions available) is set via the operator ::set_system('no_object_result',<Result>), the behavior in case of empty region is set via ::set_system('empty_region_result',<Result>). If necessary an exception handling is raised.

Possible Predecessors

::threshold, ::skeleton

Possible Successors

::select_matching_lines

Module

Region processing