extract image form a buffer in a ring with labview

[faux francis]

I use two buffers in a ring for an image acquisition in order to substract two images in real time.
After the buffer in the ring I didn't succeed to extract the image with the VI substract,in order to store the image in others buffers( error 14...)in order to realise the substract operation with the 1411 imaq acquisition grabber.
Could you help me to solve this problem.

[BruceAmmons]

I would use a buffer with more than two images. Ten to thirty images would work better. Keep the array of images that you generate when you are filling the ring buffer. During acquisition, you can use IMAQ status to find out what the last completed image buffer is. You can figure out the previous image easily by subtracting one and checking for wrap when it is -1. Index these images out of the image array and feed them into the IMAQ subtract vi along with an image allocated for the result. Display your results and continue to loop.

Bruce