Compare two images and highlight the difference

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This will be a very basic algorithm just to evaluate your use case. It can be improved a lot.

(i) In your case, the first step is to identify whether there is a change or not between 2 frames. It can be identified by using a simple StandardDeviation measurement. Set a threshold for acceptable difference in deviation.

Mat prevFrame, currentFrame;

for(;;)
{
    //Getting a frame from the video capture device.
    cap >> currentFrame;

    if( prevFrame.data )
    {
         //Finding the standard deviations of current and previous frame.
         Scalar prevStdDev, currentStdDev;
         meanStdDev(prevFrame, Scalar(), prevStdDev);
         meanStdDev(currentFrame, Scalar(), currentStdDev);

          //Decision Making.
          if(abs(currentStdDev - prevStdDev) < ACCEPTED_DEVIATION)
          {
               Save the images and break out of the loop.
          }     
    }

    //To exit from the loop, if there is a keypress event.
    if(waitKey(30)>=0)
        break;

    //For swapping the previous and current frame.
    swap(prevFrame, currentFrame);
}

(ii) The first step will only identify the change in frames. In order to locate the position where the change occured, find the difference between the two saved frames using AbsDiff. Using this difference image mask, find the contours and finally mark the region with a bounding rectangle.

Hope this answers your question.

If you want to compare two image to spot the differences, I think that you can use Background Subtraction Methods, see the following tutorial: http://docs.opencv.org/master/d1/dc5/tutorial_background_subtraction.html

I am an absolute newbie in this but I find this article very similar to what my endeavors are, and that is to use OpenCV to display differences between 2 images. My goal is to be able to automatically preprocess the 2 images like scaling, rotating, etc. or whatever is needed to make one image as similar to the other in terms of ROI and then display the differences if there are any.

I was told that I could use OpenCV for this and I would appreciate any guidance on how to do this in Delphi.

I am also willing to outsource this as a paid service to get me started on this.

[IMG]http://i64.tinypic.com/2lnb7rt.jpg[/IMG] [IMG]http://i67.tinypic.com/1zbgeoh.jpg[/IMG]

This solution will help you.

    Core.absdiff(firstMat, secondMat, outputImageMat);

    List<MatOfPoint> contours = new ArrayList<>();

    Imgproc.cvtColor(outputImageMat, outputImageMat, Imgproc.COLOR_BGR2GRAY);
    Imgproc.findContours(outputImageMat, contours, new Mat(), Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);

    for (int i = 0; i < contours.size(); i++) {
        Rect rect = Imgproc.boundingRect(contours.get(i));
        Imgproc.rectangle(secondMat, new Point(rect.x, rect.y), new Point(rect.x + rect.width,
                rect.y + rect.height), new Scalar(100, 0, 0, 255), 6);
    }
    outputImage.setImageBitmap(setMatToBitmap(secondMat));