how do I perform simple pixel by pixel subtraction of data in imaqbuffer (ni-imaq)

[owais]

Hi,

I have a need to subtract two images.  Now I know this is a function in Vision, but I want to use plain old imaq.  So, I grab two images from 2 seperate NI1405 framegrabber cards using           

imgGrab (Sid, (void **)&ImaqBuffer, TRUE);
imgGrab (Sid1, (void **)&ImaqBuffer1, TRUE);

and then call a function that I wrote: absSubtractImage(imaqBuffer, imaqBuffer1):

//pixel by pixel image subtraction
//absolute value
//assuming data is laid out as follows:
//pixel 0, pixel 1, pixel 2...
//00RRGGBB, 00RRGGBB, 00RRGGBB...
int absSubtractImage(Int8 *img1, Int8 *img2)    //img1 << img2 - img1
{
    int i;
    unsigned int bufSize;
   
    //make sure that the image sizes are the same
    if(sizeof(img1) != sizeof(img2))
        return -1;
   
    bufSize = sizeof(img1)/sizeof(Int8);
   
    for(i = 0; i < bufSize; i++)
    {
        *(img1+i) = abs(*(img2+i) - *(img1+i));
    }
   
    return 0;

}

Problem is sizeof returns 4...; problem probably has to do with the fact that I am probably not dereferencing the pointers correctly.  Could someone please guide me?
Thanks
Owais

[owais]

Please ignore the above request.  The answer to the number of elements is multiplying the ROI width x ROI length x pixel depth...