expand_domain_gray — Expand the domain of an image and set the gray values in the
expanded domain.
expand_domain_gray(InputImage : ExpandedImage : ExpansionRange : )
expand_domain_gray expands the border gray values of the
domain outwards. The width of the expansion is set by the parameter
ExpansionRange. All filters in HALCON use gray values of
the pixels outside the domain depending on the filter width. 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 expanded by expand_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_domain or
change_domain) after using expand_domain_gray and
call the filter operation afterwards.
ExpansionRange 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 ExpansionRange values of half the filter
length or greater.
In combination with the filter mean_image
on images of type real we recommend to determine the value for
ExpansionRange as shown in the example below.
For speed reasons this filter uses the values from pixels within the
smallest rectangle around the dilated region.
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.
InputImage (input_object) (multichannel-)image(-array) → object (byte / int1 / int2 / uint2 / int4 / real)
Input image with domain to be expanded.
ExpandedImage (output_object) image(-array) → object (byte / int1 / int2 / uint2 / int4 / real)
Output image with new gray values in the expanded domain.
ExpansionRange (input_control) integer → (integer)
Radius of the gray value expansion, measured in pixels.
Default value: 2
Suggested values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16
Restriction: ExpansionRange >= 1
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)
Let L the perimeter of the domain. Then the runtime complexity is
approximately O(L)*ExpansionRange.
expand_domain_gray returns TRUE if all parameters are
correct. If necessary, an exception is raised.
reduce_domain,
mean_image,
dyn_threshold
Foundation