get_contour_angle_xld (Operator)

Name

get_contour_angle_xld — Calculate the direction of an XLD contour for each contour point.

Synopsis

get_contour_angle_xld(Contour : : AngleMode, CalcMode, Lookaround : Angles)

Description

get_contour_angle_xld calculates for each point of the XLD contour Contour the direction of its tangent. Two modes for the output values can be chosen: By passing 'abs' for AngleMode, the resulting angles are returned relative to the horizontal axis as angles between 0 and 2*PI (counter-clockwise). By passing 'rel', the angle difference to the previous contour point is returned. In this case the range of values is between -PI and PI, where negative values indicate a right turn and positive values indicate a left turn.

There are three different ways of calculating the tangent direction (CalcMode) of the contour point i using the contour points in the interval from i - Lookaround to i + Lookaround. By using 'range', the angle of the line segment between the first and last point of the interval is used. For 'mean', the average of all angles between consecutive points of the contour is used. Finally, for 'regress', the direction of the regression line (the least squares fit of a line to the contour points in the interval) is used. Lookaround is a measure of how strongly the contour is smoothed. The angles are returned in Angles in radians.

Parameters

Contour (input_object)	xld_cont → object
Input contour.

AngleMode (input_control)	string → (string)
Return type of the angles.
Default value: 'abs'
List of values: 'abs', 'rel'

CalcMode (input_control)	string → (string)
Method for computing the angles.
Default value: 'range'
List of values: 'range', 'mean', 'regress'

Lookaround (input_control)	integer → (integer)
Number of points to take into account.
Default value: 3
Restriction: Lookaround > 0

Angles (output_control)	real-array → (real)
Direction of the tangent to the contour points.

Parallelization Information

get_contour_angle_xld is reentrant and processed without parallelization.

Possible Predecessors

gen_contours_skeleton_xld, lines_gauss, lines_facet, edges_sub_pix

See also

get_contour_xld, get_contour_attrib_xld

Module

Foundation