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

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

fetch_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 absolute value of the difference of angles to the previous contour point is returned. The range of values in this case is between 0 and PI.

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.


Possible Predecessors

gen_contour_xld, gen_contour2_xld, lines_gauss, lines_facet, edges_sub_pix


See also

get_contour_xld, get_cont_attrib_xld



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