Rockwell Automation 5370-CVIM2 Module - Manual (Page 457)

Chapter 8
Thresholds, Filters, and Morphology
8–18
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Dilation –– This function dilates the edges of white objects (and,
conversely, erodes the edges of black objects). Thus, white objects in the
image field get larger, while black objects get smaller. Successive stages
of dilation can be used to achieve the desired effect. If it is necessary to
remove black noise from within a white object without changing the size
of the white object, the stages of dilation must be followed by an equal
number of stages of erosion.
Another effect of dilation is to ”weld” together small white objects that
are otherwise separated in the original image.
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Lin. Erosion 0 –– This function erodes white objects horizontally from
left to right. It erodes only on the left side of an object, and its effect, in
successive stages, is to eliminate thin white vertical objects (such as
lines), or, conversely, thicken thin black vertical objects, without affecting
thin horizontal objects.
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Lin. Dilation 180 –– This function dilates white objects horizontally from
right to left. It dilates only on the right side of an object, and its effect, in
successive stages, is to thicken thin white vertical objects (such as lines),
or, conversely, eliminate thin black vertical objects, without affecting thin
horizontal objects.
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White Triple Point –– This function can eliminate small white objects
from within black objects without affecting the size of the black objects.
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Black Triple Point –– This function can eliminate small black objects
from the image without affecting the size of the white objects.
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Erosion Top Triangle –– This function has an effect that is similar to the
effect of the erosion function, but not as pronounced. Thus, erosion top
triangle could be used where a smaller erosion effect is desired in one
stage. It can be used with the dilation bottom triangle function in balanced
numbers of stages, such as is described above for the erosion and dilation
functions.
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Dilation Bottom Triangle –– This function has an effect that is similar to
the effect of the dilation function, but not as pronounced. Thus, dilation
top triangle could be used where a smaller dilation effect is desired in one
stage. It can be used with the erosion top triangle function in balanced
numbers of stages, such as is described above for the erosion and dilation
functions.
Look at the white features and black background in Figure 8.10 (page 8–14).
Notice that the black background contains white noise. The morphology
filtering function can be used, in this case, to remove the noise from the
background.