Rockwell Automation 5370-CVIM2 Module User 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.