National Instruments Image Acquisition Software - Manual (Page 28)

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.
After imgGrabSetup , 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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