Справочник Пользователя для National Instruments Image Acqusition Software NI-IMAQdx

transferred from the camera to system memory. In all video modes, the ROI 
specifies the amount of data decoded by the driver while acquiring into a 
user buffer. 

By default, the driver transfers the entire image. Specify a smaller ROI for 
the following reasons:

•

To acquire only the necessary subset of data

•

To increase the acquisition speed by reducing the amount of data 
transferred and/or decoded

•

To allow for multiple simultaneous acquisitions by reducing 
bandwidth usage

Although you can specify an ROI of any size, the NI-IMAQdx software coerces the 

ROI into one that is more compatible for the given camera. Refer to Chapter 3, 

, for more information about defining an ROI for scalable 

images.

The pixel format specifies the source type of the image format. Different 
pixel formats decode into different image types. Refer to the 

 

section for more information.

After configuring and starting your acquisition, the camera sends data to 
the internal buffers. To process the acquired image data, you must copy the 
data from the internal buffer into your user buffer.

Before starting the acquisition, you must allocate a user buffer in addition 
to configuring internal buffers. The driver copies or decodes image data 
from the internal buffer into the user buffer during acquisition. Then, 
process and analyze the image in the user buffer.

When acquiring data into an image, the driver resizes and casts the image 
as needed. However, if you acquire data into a user buffer, you must allocate 
enough space for one decoded image.

Unlike internal buffers, you are responsible for destroying user buffers.