VB using multiple regions

[Steverino]

I have an app written in VB6 where I have placed multiple ROIs on the image. I wish to measure the brightness in each ROI.

I know I can do this using a light meter in a loop. However, is there a way to measure all of the ROIs at one time?

Thanks!

[gregstoll]

Steverino -

If you look at the Machine Vision source code for LightMeterRectangle (found in <National Instruments>\Vision\Source\MSVB\MachineVision\) you can see that all it's doing is converting the rectangle to a mask and then calling CWIMAQVision.Histogram2.  If you want to measure the total brightness over a whole ROI, you can do a similar thing - simply call RegionsToMask to get a mask image and then call CWIMAQVision.Histogram2 with that mask image.

Alternatively, you can look at CWIMAQVision.RegionsProfile - this returns a report for each contour in the region.

Hope this helps!

Greg Stoll

Vision R&D
National Instruments

[Steverino]

What if I had multiple regions in an image and wanted to do more than measure light intensity?

For example, suppose I wanted to perform autothresholding such as clustering. I would need to restrict processing to each region else the results might be incorrect if the region were significantly different from the image as a whole.

How do I step through each region, do the image processing, and extract measurements for each region? Do you have code or pseudo-code that does this?

Thanks!

Message Edited by Steverino on 10-07-2008 05:19 PM