local_max_contours

local_max_contours_xld ( Contours, Image : LocalMaxContours : MinPercent, MinDiff, Distance : )

Select XLD contours with a local maximum of gray values.

local_max_contours_xld selects XLD contours from the contours passed in Contours, which have a local maximum in gray values across the direction of the contour. In order to be selected, at least MinPercent of the contour points must have a local maximum perpendicular to the direction of the contour. The contours' direction is determined by fitting a regression line through five neighboring points of the contour. In order to decide whether there is a local maximum for a contour point, a gray value profile that is Distance points wide and perpendicular to the contour is computed on both sides of the contour. If the gray value at the countour point is at least MinDiff larger than the gray value at at least one point on each side of the profile, the contour point is labeled as a local maximum. The selected contours are returned in LocalMaxContours.

Parameters

`Contours` (input_object)	xld_cont-array `->` object
XLD contours to be examined.

`Image` (input_object)	image `->` object : byte
Corresponding gray value image.

`LocalMaxContours` (output_object)	xld_cont-array `->` object
Selected contours.

`MinPercent` (input_control)	number `->` integer / real
Minumum percentage of maximum points.
Default value: 70
Suggested values: 60, 70, 75, 80, 85, 90, 95
Restriction: `(0.0 <= MinPercent) && (MinPercent <= 100.0)`

`MinDiff` (input_control)	integer `->` integer
Minimum amount by which the gray value at the maximum must be larger than in the profile.
Default value: 15
Suggested values: 5, 8, 10, 12, 15, 20
Restriction: `(0 <= MinDiff) && (MinDiff <= 255)`

`Distance` (input_control)	integer `->` integer
Maximum width of profile used to check for maxima.
Default value: 4
Suggested values: 2, 3, 4, 5, 6
Restriction: `Distance >= 1`

Parallelization Information

local_max_contours_xld is reentrant and processed without parallelization.

Possible Predecessors

gen_contours_skeleton_xld, lines_gauss, lines_facet, edges_sub_pix

Possible Successors

gen_polygons_xld

See also

smooth_contours_xld

Module

Sub-pixel operators