Chapter 3 Programming with NI-IMAQ
NI-IMAQ User Manual 3-8
©
National Instruments Corporation
The sample then calls a process function to analyze the image. When the
program is finished, it calls imgClose with the interface handle and sets
the freeResources flag to TRUE. This instructs NI-IMAQ to free all of the
resources associated with this interface, which releases the session as well
as the memory buffer allocated by imgSnap.
High-Level Grab Functions
A grab is a continuous high-speed acquisition of data to a single buffer in
host memory. Grab functions include imgGrabSetup, imgGrab and
imgGrabArea. You can use these functions to perform an acquisition that
loops continually on one buffer. A copy of the acquisition buffer is
obtained by grabbing a copy to a separate buffer. To use these functions,
you must have a valid session handle.
Calling imgGrabSetup initializes a session for a grab acquisition.
AfterimgGrabSetup, each successive grab will copy the last acquired
buffer into a user buffer where you can perform processing on the image. A
grab is appropriate for high-speed applications where you need processing
performed on only one image at a time. Figure 3-3 illustrates a typical grab
programming order.
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