mod_para_xld ( Parallels, Image : ModParallels, ExtParallels : Quality, MinGrey, MaxGrey, MaxStandard : )

Extract parallel XLD polygons enclosing a homogeneous area.

mod_para_xld selects XLD parallels enclosing homogeneous areas from the input parallels Parallels. The parameter Image contains the corresponding gray value image.

Only parallels having a quality factor larger than Quality are examined. The algorithm builds parallel cross sections one pixel apart, and parallel to the line segments in the area of overlap between two parallel line segments.

In the first iteration, the mean gray value for each of the lines in the cross section is calculated. In the second iteration, the standard deviations of the gray values along each line are computed.

If the mean gray value of an area between parallel lies in the interval [MinGrey,MaxGrey], and if the mean of all standard deviations is smaller than the upper threshold MaxStandard, the corresponding parallels are returned as modified parallels in ModParallels.

In a second step, all polygon segments adjacent to parallels bordering homogeneous areas are checked for homogeneity. To do so, a rectangle having the witdth of the last area anclosed by a modified parallel is constructed, and checked for homogeneity using the algorithm described above. This process is continued as long as there are adjacent polygon segments. The polygons thus found are returned as extended parallels in ExtParallels.


Parameters

Parallels (input_object)
xld_para-array -> object
Input XLD parallels.

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

ModParallels (output_object)
xld_mod_para-array -> object
Modified XLD parallels.

ExtParallels (output_object)
xld_ext_para-array -> object
Modified XLD parallels.

Quality (input_control)
number -> real / integer
Minimum quality factor (measure of parallelism).
Default value: 0.4
Suggested values: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6
Restriction: (0.0 <= Quality) && (Quality <= 1.0)

MinGrey (input_control)
integer -> integer
Minimum mean gray value.
Default value: 160
Suggested values: 80, 100, 120, 140, 160, 180
Restriction: (0 <= MinGrey) && (MinGrey <= 255)

MaxGrey (input_control)
integer -> integer
Maximum mean gray value.
Default value: 220
Suggested values: 140, 160, 180, 200, 220, 240
Restriction: ((0 <= MaxGrey) && (MaxGrey <= 255)) && (MaxGrey >= MinGrey)

MaxStandard (input_control)
number -> real / integer
Maximum allowed standard deviation.
Default value: 10.0
Suggested values: 5.0, 10.0, 15.0, 20.0
Restriction: MaxStandard >= 0.0


Possible Predecessors

parallels_xld


Possible Successors

max_parallels_xld


See also

info_para_xld



Copyright © 1996-1997 MVTec Software GmbH