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Chapter 5 Performing Machine Vision Tasks
© National Instruments Corporation 5-31 IMAQ Vision for Visual Basic User Manual
By default, CWIMAQVision.ReadDataMatrixBarcode automatically
detects the type of barcode to read. You can improve the performance of the
function by specifying the type of barcode in the application. IMAQ Vision
supports Data Matrix types ECC 000 to ECC 140, and ECC 200.
Read PDF417 Barcode
Use CWIMAQVision.ReadPDF417Barcode to read values encoded in a
PDF417 barcode.
By default,
CWIMAQVision.ReadPDF417Barcode automatically locates
one or multiple PDF417 barcodes in an image. However, you can improve
the inspection performance by locating the barcodes using one of the
techniques described in the Instrument Reader Measurements section,
and then passing in Regions of the locations into
CWIMAQVision.ReadPDF417Barcode.
Tip If you need to read only one barcode per image, set the SearchMode parameter to
cwimaqBarcode2DSearchSingleConservative to increase the speed of the method.
Display Results
You can display the results obtained at various stages of the inspection
process on the window that displays the inspection image by overlaying
information about an image. The software attaches the information that you
want to overlay to the image, but it does not modify the image.
Access overlays using the
CWIMAQImage.Overlays property. The
CWIMAQOverlays collection contains a single CWIMAQOverlay
object that you can access using
CWIMAQImage.Overlay(1).
Note The CWIMAQImage.Overlays collection does not support usual collection
methods—such as
Add, Remove, and RemoveAll—because they are reserved for
future use.
Use the following methods on the CWIMAQOverlay object to overlay
search regions, inspection results, and other information, such as text and
pictures. Overlays on a viewer image are automatically updated when you
call one of these methods.
•
DrawLine—Overlays a CWIMAQLine object on an image.
•
DrawConnectedPoints—Overlays a CWIMAQPoints collection
and draws a line between sequential points.