Operator Reference

expand_domain_grayexpand_domain_grayExpandDomainGrayExpandDomainGrayexpand_domain_gray (Operator)

expand_domain_grayexpand_domain_grayExpandDomainGrayExpandDomainGrayexpand_domain_gray — Expand the domain of an image and set the gray values in the expanded domain.

Signature

expand_domain_gray(InputImage : ExpandedImage : ExpansionRange : )

Description

expand_domain_grayexpand_domain_grayExpandDomainGrayExpandDomainGrayexpand_domain_gray expands the border gray values of the domain outwards. The width of the expansion is set by the parameter ExpansionRangeExpansionRangeExpansionRangeexpansionRangeexpansion_range, which describes the expansion radius in pixels. All filters in HALCON which are applied to the image domain also include the gray values of a certain number of pixels, depending on the filter size, outside of the image domain in their calculation. This may lead to undesirable side effects especially in the border region of the domain. For example, if the foreground (domain) and the background of the image differ strongly in brightness, the result of a filter operation may lead to undesired darkening or brightening at the border of the domain. In order to avoid this drawback, the domain is artificially expanded by expand_domain_grayexpand_domain_grayExpandDomainGrayExpandDomainGrayexpand_domain_gray in a preliminary stage, copying the gray values of the border pixels to the outside of the domain. In addition, the domain itself is also expanded to reflect the newly set pixels. Therefore, in many cases it is reasonable to reduce the domain again (reduce_domainreduce_domainReduceDomainReduceDomainreduce_domain or change_domainchange_domainChangeDomainChangeDomainchange_domain) after using expand_domain_grayexpand_domain_grayExpandDomainGrayExpandDomainGrayexpand_domain_gray and call the filter operation afterwards. ExpansionRangeExpansionRangeExpansionRangeexpansionRangeexpansion_range should be set to a value high enough to make sure the whole region including its dilatation through the filter mask has initialized values. Usually this leads to ExpansionRangeExpansionRangeExpansionRangeexpansionRangeexpansion_range values of half the filter length or greater. In combination with the filter mean_imagemean_imageMeanImageMeanImagemean_image on images of type real we recommend to determine the value for ExpansionRangeExpansionRangeExpansionRangeexpansionRangeexpansion_range as shown in the example below. For speed reasons this filter uses the values from pixels within the smallest rectangle around the dilated region.

Attention

Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.

Execution Information

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Automatically parallelized on tuple level.

Parameters

InputImageInputImageInputImageinputImageinput_image (input_object) (multichannel-)image(-array) → object (byte / int1 / int2 / uint2 / int4 / real)

Input image with domain to be expanded.

ExpandedImageExpandedImageExpandedImageexpandedImageexpanded_image (output_object) image(-array) → object (byte / int1 / int2 / uint2 / int4 / real)

Output image with new gray values in the expanded domain.

ExpansionRangeExpansionRangeExpansionRangeexpansionRangeexpansion_range (input_control) integer → (integer)

Radius of the gray value expansion, measured in pixels.

Default: 2

Suggested values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16

Restriction: ExpansionRange >= 1

Example (HDevelop)

read_image(Fabrik, 'fabrik')
gen_rectangle2(Rectangle_Label,243,320,-1.55,62,28)
reduce_domain(Fabrik, Rectangle_Label, Fabrik_Label)
* Character extraction without gray value expansion:
MaskSize := 31
mean_image(Fabrik_Label,Label_Mean_normal,MaskSize, MaskSize)
dyn_threshold(Fabrik_Label,Label_Mean_normal,Characters_normal,10,'dark')
dev_display(Fabrik)
dev_display(Characters_normal)
* The characters in the border region are not extracted !
stop()
* Character extraction with gray value expansion:
get_domain (Fabrik_Label, Domain)
expand_domain_gray (Fabrik_Label, Expanded_Fabrik_Label, MaskSize)
get_domain (Expanded_Fabrik_Label, Expanded_Domain)
shape_trans (Expanded_Domain, RegionRect, 'rectangle1')
difference (RegionRect, Expanded_Domain, Region_Difference)
overpaint_region (Expanded_Fabrik_Label, Region_Difference, 0, 'fill')
reduce_domain (Expanded_Fabrik_Label, Domain, Reduced_Expanded_Fabrik_Label)
mean_image (Reduced_Expanded_Fabrik_Label, Label_Mean_Expanded,\
MaskSize, MaskSize)
dyn_threshold(Fabrik_Label,Label_Mean_Expanded,\
Characters_expanded,10,'dark')
dev_display(Fabrik)
dev_display(Characters_expanded)

Complexity

Let L the perimeter of the domain. Then the runtime complexity is approximately O(L)*ExpansionRangeExpansionRangeExpansionRangeexpansionRangeexpansion_range.

Result

expand_domain_grayexpand_domain_grayExpandDomainGrayExpandDomainGrayexpand_domain_gray returns 2 ( H_MSG_TRUE) if all parameters are correct. If necessary, an exception is raised.

Possible Predecessors

reduce_domainreduce_domainReduceDomainReduceDomainreduce_domain

Possible Successors

reduce_domainreduce_domainReduceDomainReduceDomainreduce_domain, mean_imagemean_imageMeanImageMeanImagemean_image, dyn_thresholddyn_thresholdDynThresholdDynThresholddyn_threshold

Module

Foundation

Operators