Read pdf417 barcode, Display results, Read pdf417 barcode -31 – National Instruments IMAQTM User Manual

Page 83: Display results -31

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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.

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