Image Acquisitionand Proces

Image Acquisition 51
use a property node 1 (Figure 3.6). The property node example in Figure 3.8 returns
the image type of the session, which is determined by either camera initialization,
or is set dynamically. This image type value can then be passed to IMAQ Create,
reserving the correct number of bytes per pixel for the acquired image data.
FIGURE 3.7 Simple snap example.
3.2.1 SNAP
Acquiring an image using IMAQ Snap is the simplest type of image acquisition
(Figure 3.7). Used for slow acquisition rates, IMAQ Snap requires just three steps
to execute: initialize, acquire and close. To initialize the IMAQ session, the interface
name (or the camera name in the case of an FireWire interface) is input to IMAQ Init,
which opens the camera by loading and parsing its icd Þle from disk (as determined
by the Measurement and Automation Explorer), and opening an IMAQ session
(Figure 3.8).
FIGURE 3.8 Simple snap example — wiring diagram.
The IMAQ session refnum is then fed into a property node, which is set to
determine the image type of the camera interface. The dataspace for the image is
1
The FireWire image acquisition VIs do not use a property node for setting acquisition properties. Use
IMAQ1394 Attribute to set properties, and IMAQ1394 Attribute Inquiry to read properties.