Rockwell Automation 5370-CVIM2 Module - Manual (Page 202)

5 Chapter Chapter 6
Reference Tools
6–43
Scale To Selections
The Nearest Neighbor and Neighborhood Average “scale to” selections,
shown in Figure 6.37, have no effect when the X scale and Y scale selections
are both 1:1 –– they are applicable only when the X scale and/or Y scale
selections are other than 1:1.
Figure 6.37 Scale To Selections
Neighborhood Average –– This is the default selection. The template match
is based on the average gray value of the scaled neighborhood.
Nearest Neighbor –– The template match is based on picking the value of the
pixel that is in the upper–left corner of a block of pixels, such as “45” in
block “A” of Figure 6.35 (page 6–41). (In this case, “nearest neighbor”
would result in a single pixel with a gray scale value of 45.) Nearest neighbor
is a somewhat faster approximation for template matching purposes than
neighborhood average, but gives a less accurate approximation of the image.
Pixel Error Parameter Selections
The Ignore

Pixel Errors
 and
Max. RMS

Pixel Error parameters
determine, for the purposes of template matching, the extent to which the
gray values of the pixels in the search image are permitted to deviate from
the gray values of the pixels in the feature image and still achieve a
successful template match.
Ignore
Pixel Errors  –– This parameter sets the value at (or below)
which pixel gray value mismatches (“pixel errors”) are ignored during the
search operation. The default setting is 10.
The term “error” refers to any difference between the gray value of a pixel in
the feature image and the gray value of the corresponding pixel in the search
image. For example, if the gray value of a particular feature image pixel were
20 and the corresponding search image pixel were 25, the error would be 5.
With the “
Ignore ” setting at the default value (10), the reference window
would ignore this error. If, however, the corresponding search image pixel
were 31, the error would be 11, and the reference window would recognize
that error.