Detect translation in ROI

[bthiam]

I know there's a command imaqDetectRotation in IMAQ. Is there a similar function to detect translation of an ROI? If not, what would your suggestions be for me to do so making use of available commands in IMAQ?

[Julie S]

There isn't a dedicated function to detecting the translation of an ROI, because generally the part that is rotating inside the ROI is what you are more interested in determining the rotation angle of. Have you looked at the example that comes with the Vision software, entitled Rotating Part Example in the folder C:\Program Files\National Instruments\LabVIEW 7.0\examples\Vision\3. Applications ? This shows how to use the Rotation detection and then apply the results to rotate the ROI. Could you process your image in this way instead?
Hope this helps -
Julie S
Applications Engineer
National Instruments

[bthiam]

For my application, I am more interested in whether the ROI moved than rotate. One of the ways for me to explore is the Centroid function. Would you have any examples in CVI for that?

[Julie S]

Here is an example that finds the Centroid of an image in C++:
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3DA1D56A4E034080020E74861&p_node=DZ52000_US&p_source=External

-Julie

[bthiam]

Thanks a lot Julie. I realise Centroid is not a very robust way to track translation in motion. But I really appreciate your help a lot. Thanks.

[BruceAmmons]

If you are looking for translation of the image, not the ROI, the best thing to use is probably pattern matching. It would only work for a static object, but you could train an area and monitor its coordinates using pattern matching.

Bruce