expand_grayExpandGrayExpandGrayexpand_grayexpand_gray🔗

Short description🔗

expand_grayExpandGrayExpandGrayexpand_grayexpand_gray — Fill gaps between regions (depending on gray value or color) or split overlapping regions.

Signature🔗

expand_gray( region Regions, image Image, region ForbiddenArea, out region RegionExpand, string Iterations, string Mode, integer Threshold )

Description🔗

expand_grayExpandGray closes gaps between the input regions, which resulted from the suppression of small regions in a segmentation operator, (mode 'image'"image"), for example, or separates overlapping regions 'region'"region"). Both uses result from the expansion of regions. The operator works by adding a one pixel wide “strip” to a region, in which the gray values or color are different from the gray values or color of neighboring pixels on the region’s border by at most Thresholdthresholdthreshold (in each channel). For images of type 'cyclic'"cyclic" (e.g., direction images), also points with a gray value difference of at least \(255 - \textrm{Threshold}\) are added to the output region.

The expansion takes place only in regions, which are designated as not “forbidden” (parameter ForbiddenAreaforbiddenAreaforbidden_area). The number of iterations is determined by the parameter Iterationsiterationsiterations. By passing 'maximal'"maximal", expand_grayExpandGray iterates until convergence, i.e., until no more changes occur. By passing 0 for this parameter, all non-overlapping regions are returned. The two modes of operation ('image'"image" and 'region'"region") are different in the following ways:

'image'"image" The input regions are expanded iteratively until they touch another region or the image border, or the expansion stops because of too high gray value differences. Because expand_grayExpandGray processes all regions simultaneously, gaps between regions are distributed evenly to all regions with a similar gray value. Overlapping regions are split by distributing the area of overlap evenly to both regions.
'region'"region" No expansion of the input regions is performed. Instead, only overlapping regions are split by distributing the area of overlap evenly to regions having a matching gray value or color.

Attention🔗

Because regions are only expanded into areas having a matching gray value or color, usually gaps will remain between the output regions, i.e., the segmentation is not complete.

Execution information🔗

Execution information

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Processed without parallelization.

Parameters🔗

Regionsregionsregions (input_object) region(-array) → objectHObjectHRegionHObjectHobject

Regions for which the gaps are to be closed, or which are to be separated.

Imageimageimage (input_object) (multichannel-)image → object (byte / cyclic)HObject (byte / cyclic)HImage (byte / cyclic)HObject (byte / cyclic)Hobject (byte / cyclic)

Image (possibly multi-channel) for gray value or color comparison.

ForbiddenAreaforbiddenAreaforbidden_area (input_object) region → objectHObjectHRegionHObjectHobject

Regions in which no expansion takes place.

RegionExpandregionExpandregion_expand (output_object) region(-array) → objectHObjectHRegionHObjectHobject *

Expanded or separated regions.

Iterationsiterationsiterations (input_control) string → (string / integer)HTuple (HString / Hlong)HTuple (string / int / long)Union[int, str]Htuple (char* / Hlong)

Number of iterations.

Default: 'maximal'"maximal"
Suggested values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 'maximal'
Value range: 1 ≤ Iterations ≤ 500 (lin)
Minimum increment: 1
Recommended increment: 1

Modemodemode (input_control) string → (string)HTuple (HString)HTuple (string)strHtuple (char*)

Expansion mode.

Default: 'image'"image"
List of values: 'image', 'region'"image", "region"

Thresholdthresholdthreshold (input_control) integer(-array) → (integer)HTuple (Hlong)HTuple (int / long)MaybeSequence[int]Htuple (Hlong)

Maximum difference between the gray value or color at the region’s border and a candidate for expansion.

Default: 3232
Suggested values: 5, 10, 15, 20, 25, 30, 40, 505, 10, 15, 20, 25, 30, 40, 50
Value range: 1 ≤ Threshold ≤ 255 (lin)
Minimum increment: 1
Recommended increment: 5

Example🔗

(C)

read_image(&Image,"fabrik")\;
disp_image(Image,WindowHandle)\;
regiongrowing(Image,&RawSegments,3,3,6.0,100)\;
set_colored(WindowHandle,12)\;
disp_region(RawSegments,WindowHandle)\;
expand_gray(RawSegments,Image,EMPTY_REGION,&Segments,"maximal","image",24)\;
disp_region(Segments,WindowHandle)

(C++)

#include "HIOStream.h"
#if !defined(USE_IOSTREAM_H)
using namespace std\;
#endif
#include "HalconCpp.h"
using namespace Halcon\;

int main (int argc, char *argv[])
{
  HImage   image (argv[1])\;
  HRegion  empty_region\;
  HWindow  win\;
 image.Display (win)\;
 HRegionArray seg = (image >= 100).Connection ()\;
 seg.Display (win)\;
  HRegionArray exp = seg.ExpandGray1 (image, empty_region,
                                      "maximal", "image", 32)\;
  win.SetDraw ("margin")\;
  win.SetColored (12)\;
  exp.Display (win)\;
  win.Click ()\;
 return (0)\;
}

Result🔗

expand_grayExpandGray always returns the value 2 (H_MSG_TRUE). The behavior in case of empty input (no regions given) can be set via set_system('no_object_result',<Result>), the behavior in case of an empty input region via set_system('empty_region_result',<Result>), and the behavior in case of an empty result region via set_system('store_empty_region',<'true'/'false'>). If necessary, an exception is raised.

Combinations with other operators🔗

Combinations

Possible predecessors

connectionConnection, regiongrowingRegiongrowing, pouringPouring, class_ndim_normClassNdimNorm

Possible successors

select_shapeSelectShape

Module🔗

Foundation