union_cont_xld ( Contours : UnionContours : MaxDist, MaxDiff, Percent, Mode : )

Merger neighboring XLD contours having a similar direction.

union_cont_xld merges neighboring XLD contours Contours if certain criteria are fulfilled. The merging is not done recursively, and only between two contours. Thus, subsequent calls to the operator with the same parameters may result in additional mergings.

Two contours are merged if the shortest distance between their end points (end points are the projections of the contours first and last points onto its regression line) is smaller than MaxDist, and if the difference in direction (i.e., the regression lines' direction) is smaller than MaxDiff (radians).

If only one of the criteria is fulfilled the decision on merging can be influenced by the weighting factor Percent, which allows the exceeding of one limit to be balanced by the other value remaining below the limit by the same amount. The end point distance is weighted by Percent, while the directional difference is weighted by 100 - Percent.

If, for example, two contours have an end point distance of 5.0 and a directional difference of 0.5 (with the limits chosen being MaxDist = 4.0 und MaxDiff = 0.625), both values differ from the limits by 25. By choosing Percent = 60, the larger end point distance is weigthed more than the smaller directional difference, and thus the contours are not merged. Contrary, if Percent = 40 is chosen, the contours are merged.

For Percent = 100, only the end point distance is taken into account, while for Percent = 0 is used. If Percent = 50 both criteria are equally valid.

In case there are parallel contours, there is a danger of merging neighboring contours. If this is to be avoided Mode = 'noparallel' has to be chosen, while otherwise Mode = 'paralleltoo' suffices. For Mode = 'every', contours are merged unconditionally. All other parameters have no influence in this case.

The parameters of the regression line are calculated anew for merged contours.


Attention

Before the contour parameters can be returned by cont_info_xld, the parameters of the regression line to the contour must be calculated by calling regress_cont_xld.


Parameters

Contours (input_object)
xld_cont-array -> object
Input XLD contours.

UnionContours (output_object)
xld_cont-array -> object
Output XLD contours.

MaxDist (input_control)
real -> real
Maximum distance of the contours' endpoints.
Default value: 5.0

MaxDiff (input_control)
angle.rad -> real
Maximum difference in direction.
Default value: 0.5

Percent (input_control)
real -> real
Weighting factor for the two selection criteria.
Default value: 50.0

Mode (input_control)
string -> string
Should parallel contours be taken into account?
Default value: 'noparallel'
List of values: 'noparallel', 'paralleltoo', 'every'


Possible Predecessors

regress_cont_xld


See also

get_contour_xld, get_cont_attrib_xld, gen_contour_xld, gen_contour2_xld, lines_gauss, lines_facet, edges_sub_pix, cont_info_xld



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