Where in my code have I broken the Mat equivalence rule?

I'm trying to achieve background subtraction in openCV 2.2 using the cv namespace (Qt4.7). I have the following code which compiles fine but when running the program breaks because one mat doesn't equal the other but I can't find out where it is and I'm currently going through the API reference to try and find it.

           cvtColor( mcolImage, mcolImage, CV_BGR2RGB);
           cvtColor( mcolIm开发者_JAVA百科age, gscaleImage, CV_RGB2GRAY);

           acc = Mat(Size(440,320), CV_32FC3);
           accSQ = Mat(Size(440,320), CV_32FC3);

           //we accumulate into a Mat to get an frames average
           Mat avg;
           accumulateWeighted(gscaleImage, acc, 3.0, Mat());
           accumulateSquare(gscaleImage, accSQ, Mat());
           multiply(acc, acc, avg, 1);

           Mat sigma, sigmaSQRT;
           subtract(accSQ, avg, sigmaSQRT, Mat());
           sqrt(sigmaSQRT, sigma); //Holds the standard deviation

           Mat fgImage; //hold the foreground image
           cv::absdiff(avg,gscaleImage, fgImage);

           //GaussianBlur(gscaleImage, gscaleImage, Size(7,7), 2, 2 );

           Mat buff ;
           //convert to black and white
           threshold(fgImage, buff, 75, THRESH_BINARY, 100);

           dilate(buff, buff, Mat(3, 3, CV_8UC1), Point(-1, -1), 1, BORDER_CONSTANT, Scalar(1.0, 1.0, 1.0, 0));
           erode(buff, buff, Mat(3, 3, CV_8UC1), Point(-1, -1), 1, BORDER_CONSTANT, Scalar(1.0, 1.0, 1.0, 0));

           //rectangle(gscaleImage, cvPoint(100, 300), cvPoint(200, 100), cvScalar(255, 255, 255, 0), 1);

           QImage colImagetmp((uchar*)mcolImage.data, mcolImage.cols, mcolImage.rows, mcolImage.step,
                              QImage::Format_RGB888 ); //Colour

           QImage gscaleImagetmp ((uchar*)gscaleImage.data, gscaleImage.cols, gscaleImage.rows, gscaleImage.step,
                              QImage::Format_Indexed8); //Greyscale. I hope

           QImage bwImagetmp((uchar*)buff.data, buff.cols, buff.rows, buff.step,
                            QImage::Format_Indexed8);

           //Setup a colour table for the greyscale image
           QVector<QRgb> colorTable;
           for (int i = 0; i < 256; i++) colorTable.push_back(qRgb(i, i, i));
           bwImagetmp.setColorTable(colorTable);
           gscaleImagetmp.setColorTable(colorTable);


           ui.intDisplay->setPixmap(QPixmap::fromImage(bwImagetmp));
           ui.bwDisplay->setPixmap(QPixmap::fromImage(gscaleImagetmp));
           ui.colDisplay->setPixmap( QPixmap::fromImage(colImagetmp ));

Thanks for the help in advanced.

Edit:

After going through the code I found that the absdiff(avg, gscaleImage, fgImage); is where the program is crashing. I think it maybe crashing on the second parameter but not sure.

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I solved it (I think) by declaring a new temporary Mat and converting that specifically (using avg.convert() ) to match the gscaleImage type and size.