| Operators |
segment_contours_xld — Segment XLD contours into line segments and circular or elliptic arcs.
segment_contours_xld(Contours : ContoursSplit : Mode, SmoothCont, MaxLineDist1, MaxLineDist2 : )
segment_contours_xld segments the input contours Contours into lines if Mode='lines', into lines and circular arcs if Mode='lines_circles', or into lines and elliptic arcs if Mode='lines_ellipses'. The segmented contours are returned in ContoursSplit. The information on whether an output contour represents a line or a circular or elliptic arc is done via the global contour attribute 'cont_approx' (see get_contour_global_attrib_xld). If 'cont_approx'=-1, the contour is best approximated by a line segment, if 'cont_approx'=0, by an elliptic arc, and if 'cont_approx'=1, by a circular arc.
segment_contours_xld first approximates the input contours by polygons. With this, the contours are oversegmented in curved areas. After this, neighboring line segments are substituted by circular or elliptic arcs, respectively, if the contour can be approximated better by an arc. If SmoothCont is set to a value > 0, the input contours are first smoothed (see smooth_contours_xld). This can be necessary to prevent very short segments in the polygonal approximation and to achieve a more robust fit with circular or elliptic arcs, because the smoothing suppresses outliers on the contours.
The initial polygonal approximation is done by using the Ramer algorithm (see gen_polygons_xld) with a maximum distance of MaxLineDist1. After this, circular or elliptic arcs are fit into neighboring line segments. If the maximum distance of the resulting arc to the contour is smaller than the maximum distance of the two line segments, the two line segments are replaced with the arc. This procedure is iterated until no more changes occur.
After this, the parts of the contour that are still approximated by line segments are again segmented with a polygonal approximation with maximum distance MaxLineDist2, and the newly created line segments are merged to circular or elliptical arcs where possible. Obviously, this changes the output only if MaxLineDist2 < MaxLineDist1. This two-step approach is more efficient than a one-step approach with MaxLineDist2, since fewer line segments are generated in the first step, and hence the circle or ellipse fit has to be performed less often. Therefore, parts of the input contours that can be approximated by long arcs can be found more efficiently. In the second step, parts of the input contours that can be approximated by short arcs are found and the end parts of long arcs are refined.
The resulting contours are at least 3 pixel long and contain at least 6 successive points of the input contour. All input contours with a length less than 3 pixel or with less than 6 contour points are copied to the output contours without modifications.
Contours to be segmented.
Segmented contours.
Mode for the segmentation of the contours.
Default value: 'lines_circles'
List of values: 'lines', 'lines_circles', 'lines_ellipses'
Number of points used for smoothing the contours.
Default value: 5
Suggested values: 0, 3, 5, 7, 9
Restriction: SmoothCont == 0 || SmoothCont >= 3 && odd(SmoothCont)
Maximum distance between a contour and the approximating line (first iteration).
Default value: 4.0
Suggested values: 1.0, 1.5, 2.0, 2.5, 3.0, 3.5
Restriction: MaxLineDist1 >= 0.0
Maximum distance between a contour and the approximating line (second iteration).
Default value: 2.0
Suggested values: 1.0, 1.5, 2.0, 2.5, 3.0, 3.5
Restriction: MaxLineDist2 >= 0.0
read_image (Image, 'pumpe')
edges_sub_pix (Image, Edges, 'canny', 1.5, 15, 40)
segment_contours_xld (Edges, ContoursSplit, 'lines_circles', 5, 4, 2)
count_obj (ContoursSplit, Number)
gen_empty_obj (Lines)
gen_empty_obj (Circles)
for I := 1 to Number by 1
select_obj (ContoursSplit, Contour, I)
get_contour_global_attrib_xld (Contour, 'cont_approx', Type)
if (Type == -1)
concat_obj (Lines, Contour, Lines)
else
concat_obj (Circles, Contour, Circles)
endif
endfor
fit_line_contour_xld (Lines, 'tukey', -1, 0, 5, 2, RowBegin, ColBegin, \
RowEnd, ColEnd, Nr, Nc, Dist)
fit_circle_contour_xld (Circles, 'atukey', -1, 2, 0, 3, 2, Row, Column, \
Radius, StartPhi, EndPhi, PointOrder)
gen_contours_skeleton_xld, lines_gauss, edges_sub_pix
fit_line_contour_xld, fit_ellipse_contour_xld, fit_circle_contour_xld, get_contour_global_attrib_xld
split_contours_xld, get_contour_global_attrib_xld, smooth_contours_xld, gen_polygons_xld
Foundation
| Operators |