National Instruments IMAQ Vision for LabWindows TM /CVI - Manual (Page 22)

Chapter 2 Getting Measurement-Ready Images
IMAQ Vision for LabWindows/CVI User Manual 2-6 ni.com
Acquiring an Image
Use one of the following methods to acquire images with a National
Instruments IMAQ device.
• Acquire a single image using imaqEasyAcquire() . When you call
this function, it initializes the IMAQ device and acquires the next
incoming video frame. Use this function for low-speed single capture
applications where ease of programming is essential.
• Acquire a single image using imaqSnap() . When you call this
function, it acquires the next incoming video frame on an IMAQ
device you have already initialized using
imgInterfaceOpen() and
i mgSessionOpen() . Use this function for high-speed single capture
applications.
• Acquire images continually through a grab acquisition. Grab functions
perform high-speed acquisitions that loop continually on one buffer.
Use
imaqSetupGrab() to start the acquisition. Use imaqGrab()
to return a copy of the current image. Use imaqStopAcquisition()
to stop the acquisition.
• Acquire a fixed number of images using a sequence acquisition.
Set up the acquisition using
imaqSetupSequence() . Use
imaqStartAcquisition() to acquire the number of images you
requested during setup. If you want to acquire only certain images,
supply
imaqSetupSequence() with a table describing the number
of frames to skip after each acquired frame.
• Acquire images continually through a ringed buffer acquisition.
Set up the acquisition using
imaqSetupRing() . Use
imaqStartAcquisition() to start acquiring images into the
acquired ring buffer. To get an image from the ring, call
imaqExtractFromRing() or imaqCopyRing() . Use
imaqStopAcquisition() to stop the acquisition.
Note You must use imgClose() to release resources associated with the image
acquisition device.
Reading a File
Use imaqReadFile() to open and read data from a file stored on your
computer into the image reference. You can read from image files stored
in several standard formats: BMP, TIFF, JPEG, PNG, and AIPD. The
software automatically converts the pixels it reads into the type of image
you pass in.