Rockwell Automation 5370-CVIM2 Module - Manual (Page 460)

5 Chapter Chapter 8
Thresholds, Filters, and Morphology
8–21
Here are the gray scale morphology functions shown in the Function
selection panel, along with a brief description of each:
•
Identity –– This operation performs no filtering effect on the image. It is
equivalent to making the gray scale morphology inactive.
•
MIN –– This function uses only the selections in the Min boxes. The
result is the minimum of the neighbors enabled in the MIN kernel.
When the Min kernel is fully configured with asterisks, the Min function
is analogous to the binary erosion function, in the sense that it makes
bright objects smaller (and dark objects larger).
•
MAX –– This function uses only the selections in the Max boxes. The
result is the maximum of the neighbors enabled in the MAX kernel.
When the Max kernel is fully configured with asterisks, the Max function
is analogous to the binary dilation function, in the sense that it makes
bright objects larger (and dark objects smaller).
•
MAX – MIN –– This function uses the selections in both the Min and the
Max boxes. It is used to detect edges, and it smoothes the image slightly.
•
(MAX + MIN) / 2 –– This function uses the selections in both the Min
and the Max boxes. The result value is the average of the Max and Min
selections.
Gray scale morphology processing uses a “kernel” structure to examine each
pixel in the image. The “kernel” structure is represented by a group of seven
boxes, as shown in the gray scale selection panel in Figure 8.13 (page 8–15).
This structure comprises a “neighborhood” of seven pixels.
Each box can contain either an asterisk (*) or a minus sign (–). An asterisk
designates the neighborhood pixels that the morphology processor will
evaluate; a minus sign designates the neighborhood pixels that the processor
will not evaluate.
Figure 8.17 (page 8–22) illustrates the relation of the kernel structure to the
matrix of pixels in the image. The pixel being examined currently is the one
under the “C” (center) box in the kernel structure. (The arrows indicate the
path of the kernel through the image matrix.)
As noted above, the morphology processor evaluates only the neighborhood
pixels under the boxes containing asterisks. It determines (and replaces the
center pixel with) the largest gray scale value of these pixels in the
MAX
kernel. Similarly, it determines (and replaces the center pixel with) the
smallest gray scale value of these neighborhood pixels in the
MIN kernel.