gen_contour_region_xld — Generate XLD contours from regions.
gen_contour_region_xld generates XLD contours
Contours from the regions given in Regions. This
operator is useful if regions have been obtained from segmentation
operations, but higher level operators, e.g., polygon approximation
and extraction of parallels, are to be performed on their
boundaries. For each connected component of the input regions a
closed contour of the boundary is generated. The parameter
Mode can take on the following values:
'center': The centers of the border pixels are used as contour points.
'border': The outer border of the border pixels is used as contour points.
'border_holes': In addition to the outer border of the input region you get the contours of all holes.
The difference between the two modes 'border' and
'center' can be seen by considering the
following region:
+-+-+
| | |
+-+-+-+-+
| | | | | +-+
+-+-+-+-+ where | | symbolizes a single pixel.
| | | | | +-+
+-+-+-+-+
| | |
+-+-+
Then, computing the contour with 'border' and
'center' results in the following two contours,
respectively:
+-+-+
| | *-*
+-+ +-+ / \
| | * *
+ + | |
| | * *
+-+ +-+ \ /
| | *-*
+-+-+
'border' 'center'
This means, for example, that contours generated with
'border' will in general have a much larger Euclidean
length (see length_xld) than contours generated with
'center'. This results from the fact that for diagonal
border elements 'border' uses two contour segments of
length 1 each, whereas 'center' uses a single segment of
length . Other features, e.g., the area (see
area_center_xld), will obviously also have different values.
Regions (input_object) region(-array) → object
Input regions.
Contours (output_object) xld_cont(-array) → object
Resulting contours.
Mode (input_control) string → (string)
Mode of contour generation.
Default value: 'border'
List of values: 'border', 'border_holes', 'center'
smooth_contours_xld,
gen_polygons_xld
gen_contour_polygon_xld,
get_region_contour
Foundation