Any examples of IMAQ Correlation

[Hansa]

Hello Folks,

I am trying to utilize "IMAQ Correlation" VI  to correlate two near identical images. But this VI takes more than 5 minutes just to process two images of size (1280 x 1024). I need to track the position/location of various particles in an image during the course of my experiment (about 300 ~400 images).

Any help or suggestion will be greatly appreciated. Thanks.

[rpursley8]

You need to input values into the Optional Rectangle input to reduce the size of the area where the cross correlation occurs.  The only other option is to reduce the resolution of the image.  Otherwise you are probably out of luck.

[Hansa]

Hi Randall,

Thanks for the reply. I did use the optional rectangle option, which was faster and resulted in all "white" pixels in that rectangle in final image (out). Generally, in mathematical expression - Normalized correlation gives the output between -1 to 1. So how should I intrepret the white pixels as? Will it be a right approach, if I make a template size of 50 x 50 pixel and peform the correlation analysis for a whole image using a loop? Any suggestion !!!

Basically, I am trying to understand how this IMAQ Correlation VI is working. I couldn't find much explation other than whatever is given in general help or IMAQ concept manual, which is not very clear.

Thanks Again.

[rpursley8]

What version of LabVIEW are you using?  Can you post the images?


Message Edited by rpursley8 on 03-06-2008 03:55 PM

[Hansa]

Thanks for reply. I am using LabView 8.5.

I had attached three images and a VI which I was trying with (LV 8.0 version).

Thanks.

[rpursley8]

Your program seemed to work fine for me.  For your image, the point of maximum correlation should be near the center, so I change the optional rectangle to that  area and then extracted those pixels to look for the location of the maximum.  I have attached it with a few changes.

Also, there are ways to parallelize the correlation function and tile them together for a larger image.  How effective this is will depend on the PC being used.  The first step is to open up the IMAQ Correlate function and go to its properties and make it reentrant in the Execution tab.  I will try to past a parallelized version based on your images over the next couple days.

Hope this helps.