mod_parallels_xld — Extract parallel XLD polygons enclosing a homogeneous area.
mod_parallels_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 performs 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 parallels lies in the interval [MinGray,MaxGray], 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 width of the last area enclosed 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.
Input XLD parallels.
Corresponding gray value image.
Modified XLD parallels.
Extended XLD parallels.
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
Minimum mean gray value.
Default value: 160
Suggested values: 80, 100, 120, 140, 160, 180
Restriction: 0 <= MinGray && MinGray <= 255
Maximum mean gray value.
Default value: 220
Suggested values: 140, 160, 180, 200, 220, 240
Restriction: 0 <= MaxGray && MaxGray <= 255 && MaxGray >= MinGray
Maximum allowed standard deviation.
Default value: 10.0
Suggested values: 5.0, 10.0, 15.0, 20.0
Restriction: MaxStandard >= 0.0