A viewer can only have one ROI associated with it at any given time, however you could store multiple ROIs in an array and apply them arbitrarily using IMAQ Set ROI or pull off different ROIs for different processing steps in your program.
Alternately, a single region can have multiple contours. Use the Group and Ungroup functions to manipulate the contours within the ROI. Take a look at the ROI descriptor data type to get an idea about the relation between an ROI and a contour.
There is a good ROI example called Region of Interest.vi in the \LabVIEW x\examples\Vision\2. Functions\Display folder. This example only manages one ROI, however you can hold down the CTRL key to draw multiple contours.
Regards,
Brent R.
Applications Engineer
National Instr
uments
