National Instruments IMAQTM 用户手册

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When you have an automated application, you need to define regions of 
interest programmatically. You can programmatically define regions by 
providing basic parameters that describe the region you want to define. You 
can specify a rotated rectangle by creating a CWIMAQRotatedRectangle 
object and setting the coordinates of the center, width, height, and rotation 
angle. You can specify an annulus by creating a CWIMAQAnnulus object 
and setting the coordinates of the center, inner radius, outer radius, start 
angle, and end angle. You can specify a point by setting its x-coordinates 
and y-coordinates. You can specify a line by setting the coordinates of the 
start and end points.

Refer to Chapter 3, 

, for more 

information about defining regions of interest.

After you set regions of inspection, locate points in the regions on which 
you can base measurements. You can locate measurement points using 
edge detection, pattern matching, color pattern matching, and color 
location.

Use the edge detection tools to identify and locate sharp discontinuities 
in an image. Discontinuities typically represent abrupt changes in pixel 
intensity values, which characterize the boundaries of objects.

SetupViewerForPointSelection

GetSelectedPointFromViewer

LightMeterPoint

SetupViewerForLineSelection

GetSelectedLineFromViewer

LightMeterLine

Table 5-1.  ROI Selection Methods to Use with CWMachineVision Methods (Continued)