Image Display

Using NI Vision with the LabVIEW Real-Time Module gives you two options for displaying images: Remote Display and RT Video Out. Use Remote Display during development and debugging to view your images from your host machine just as you would view the LabVIEW front panels of the VIs running on your LabVIEW Real-Time Module system. If your remote target has an external monitor connection, use RT Video Out to display your images on a monitor connected to your remote LabVIEW Real-Time Module system.

Remote Display

Remote Display allows you to acquire images on your remote system and view them on your host machine. Remote Display is automatically enabled when you use the LabVIEW Image Display control (available with LabVIEW 7.0 or later) or any of the NI Vision External Display VIs—such as the IMAQ WindDraw, IMAQ WindToolsShow, and IMAQ ConstructROI VIs.

Remote Display is useful for monitoring and debugging your applications that use NI Vision with the LabVIEW Real-Time Module. Familiarize yourself with how Remote Display works before using this feature.

The following details will help you prepare your application for use with Remote Display:

• Remote Display is a front-panel feature. Therefore, your LabVIEW front-panel must be open for you to see images displayed using Remote Display.
• Remote Display performs best when combined with the IMAQ Remote Display Options VI. When you display images on your remote machine, LabVIEW must send those images over your network. This process can take up a large amount of your network bandwidth, especially when transferring large images. IMAQ Remote Display Options allows you to specify compression settings for those images to reduce the network bandwidth used by the display process. In addition, compressing images may increase your display rates on slower networks.

Note  IMAQ Remote Display Options will not affect the remote display options in versions of LabVIEW prior to LabVIEW 8.0. Use the IMAQ Flatten Image Options VI instead.

• IMAQ Remote Display Options uses two types of compression algorithms. Use the lossy JPEG compression algorithm on grayscale and color images. Use the lossless Packed Binary compression algorithm on binary images.

Note  JPEG Compression may result in data degradation of the displayed image. There is no degradation of the image during processing. Test various compression settings to find the right balance for your application.

• Using Remote Display can affect the timing performance of your NI Vision VIs. Do not use Remote Display if your program contains a time-critical loop.
• Disconnecting your remote system from your host machine disables Remote Display. Disabled Remote Display VIs do not affect the performance of your application. When you reconnect your remote system and host machine, Remote Display is automatically re-enabled.
• Use RT Video Out instead of Remote Display on deployed systems. Remote Display requires a LabVIEW front panel, and deployed systems do not have a front panel. Refer to the LabVIEW Help for recommended program architecture.

Tip  Refer to the section of this appendix for more information.

RT Video Out

RT Video Out allows you to display images on a monitor that is connected to your RT target. In NI Vision, the IMAQ WindDraw and IMAQ WindClose VIs provide support for RT Video Out. To display images on a monitor connected to your RT target, input 15 for the Window Number control.

Alternately, you can use the IMAQ RT Video Out VI to display image on a monitor connected to your RT target.

Note  This feature is available only on controllers that include VESA Bios Extensions 2.0 or later, such as RT PXI controllers and NI CVS-1450 Series devices.

RT Video Out supports overlay functionality. However, the overlay text is limited to one size and one font.

This display option is not a time-bounded operation. Refer to the Determinism in Real-Time Applications section for more information about time-bounded operations.

To programmatically configure your system to use RT Video Out for displaying system images, use the IMAQ Video Out Display Mode VI. This VI allows you to set parameters for screen area, color depth, and refresh frequency.