User`s guide

7 Working with Acquired Image Data

7-10

Bringing a Single Frame into the Workspace

To bring a single frame of image data into the MATLAB workspace, use the

getsnapshot function. You can call the getsnapshot function at any time after object

creation.

This example illustrates how simple it is to use the getsnapshot function.

Create an image acquisition object — This example creates a video input object

for a Matrox device. To run this example on your system, use the imaqhwinfo

function to get the object constructor for your image acquisition device and substitute

that syntax for the following code.

vid = videoinput('matrox',1);

Bring a frame into the workspace — Call the getsnapshot function to bring a

frame into the workspace. Note that you do not need to start the video input object

before calling the getsnapshot function.

frame = getsnapshot(vid);

The getsnapshot function returns an image of the same width and height as

specified by the ROIPosition property and the same number of bands as specified

by the NumberOfBands property. In this example, the video format of the data is

RGB so the value of the NumberOfBands property is 3.

whos

Name Size Bytes Class

frame 96x128x3 36864 uint8 array

vid 1x1 1060 videoinput object

Clean up — Always remove image acquisition objects from memory, and the

variables that reference them, when you no longer need them.

delete(vid)

clear vid

For an example of using getsnapshot, see the Image Acquisition Toolbox example

Acquiring a Single Image in a Loop in the Examples list at the top of the

Image Acquisition Toolbox main Documentation Center page, or open the file

demoimaq_GetSnapshot.m in the MATLAB Editor.