National Instruments IMAQTM 用户手册

types: Codabar, Code 39, Code 93, Code 128, EAN 8, EAN 13, 
Interleaved 2 of 5, MSI, and UPCA.

Use 

CWIMAQVision.ReadDataMatrixBarcode

 to read values encoded 

in a Data Matrix barcode. This method can automatically determine the 
location of the barcode and appropriate search options for the application. 
However, you can improve the performance of the application by 
specifying control values specific to the application.

CWIMAQVision.ReadDataMatrixBarcode

 can automatically locate 

one or multiple Data Matrix barcodes in an image. However, you can 
improve the inspection performance by locating the barcodes using one of 
the techniques described in the 

 section, 

and then passing the Regions parameter into 

CWIMAQVision.ReadDataMatrixBarcode

.

If you need to read only one barcode per image, set 

CWIMAQDataMatrixOptions.SearchMode

 to 

cwimaqBarcode2DSearchSingleConservative

 to increase the speed of the method.

By default, 

CWIMAQVision.ReadDataMatrixBarcode

 determines if the 

barcode has black cells on a white background or white cells on a black 
background.

Specify round cells only if the Data Matrix cells are round and have clearly defined 

edges. If the cells in the matrix touch one another, you must set 

CellShape

 to 

cwimaqBarcode2DCellShapeSquare

.

By default, 

CWIMAQVision.ReadDataMatrixBarcode

 assumes the 

barcode cells are square. If the barcodes you need to read have round cells, 
set the 

CellShape

 member of the 

CWIMAQDataMatrixOptions

 object to 

cwimaqBarcode2DCellShapeRound

.

Set the 

BarcodeShape

 member of the 

CWIMAQDataMatrixOptions

 

object to 

cwimaqBarcode2DShapeRectangular

 or 

cwimaqBarcode2DShapeSquare

 depending on the shape of the 

barcode you need to read. 

Setting the 

BarcodeShape

 member of the 

CWIMAQDataMatrixOptions

 object to 

cwimaqBarcode2DShapeRectangular

 when the barcode you need to read is square 

reduces the reliability of the application.