©
National Instruments Corporation 3-1 NI-IMAQ User Manual
3
Programming with NI-IMAQ
This chapter contains an overview of the NI-IMAQ library, a description
ofthe programming flow of NI-IMAQ , and programmin g examples.
Flowcharts are included for the following operations: snap, grab, sequence,
ring, and StillColor acquisitions.
Introduction
The NI-IMAQ API is divided into two groups, the high-level functions
and the low-level functions. With the high-level functions, you can write
programs quickly without having to learn the details of the low-level API
and driver. The low-level functions give you finer granularity and control
over your image acquisition process, but you must understand the API and
driver in greater detail.
Note The high-level functions call low-level functions and use certain attributes that
are listed in the high-level function description in the NI-IMAQ Function
Reference Manual. Changing the value of these attributes while using low-level
functions will affect the operation of the high-level functions.

High-Level Functions

The high-level function set supports four basic types of image acquisition:
•Snap acquires a single frame or field to a buffer.
•Grab performs an acquisition that loops continually on one buffer; you
obtain a copy of the acquisition buffer by grabbing a copy to a separate
buffer that can be used for analysis.
•Sequence performs an acquisition that acquires a specified number of
buffers, then stops.
•Ring performs an acquisition that loops continually on a specified
number of buffers.
The high-level function set also allows simple triggered acquisitions and
the generation of external signals on the trigger lines.
UM.book Page 1 Monday, July 13, 1998 9:49 AM