c# Detect Rectangles in Image

Question

I'm looking to detect and get a array of Rects, one for each rectangle, in the image below. How might I do this in c#?

Basically I'm trying to scan the image taken of the screen and parse the array of windows.

Rect being some form of (xloc,yloc,xsize,ysize) Returned array: rectangles = ParseRects(image);

Answer 1

Your best option will be to use the AForge.Net library.

The following code is derived from the documentation for the ShapeChecker class, and you may want to look at the documentation to further familiarize yourself.

static void Main(string[] args)
{
    // Open your image
    string path = "test.png";
    Bitmap image = (Bitmap)Bitmap.FromFile(path);

    // locating objects
    BlobCounter blobCounter = new BlobCounter();

    blobCounter.FilterBlobs = true;
    blobCounter.MinHeight = 5;
    blobCounter.MinWidth = 5;

    blobCounter.ProcessImage(image);
    Blob[] blobs = blobCounter.GetObjectsInformation();

    // check for rectangles
    SimpleShapeChecker shapeChecker = new SimpleShapeChecker();

    foreach (var blob in blobs)
    {
        List<IntPoint> edgePoints = blobCounter.GetBlobsEdgePoints(blob);
        List<IntPoint> cornerPoints;

        // use the shape checker to extract the corner points
        if (shapeChecker.IsQuadrilateral(edgePoints, out cornerPoints))
        {
            // only do things if the corners form a rectangle
            if (shapeChecker.CheckPolygonSubType(cornerPoints) == PolygonSubType.Rectangle)
            {
                // here i use the graphics class to draw an overlay, but you
                // could also just use the cornerPoints list to calculate your
                // x, y, width, height values.
                List<Point> Points = new List<Point>();
                foreach (var point in cornerPoints)
                {
                    Points.Add(new Point(point.X, point.Y));
                }

                Graphics g = Graphics.FromImage(image);
                g.DrawPolygon(new Pen(Color.Red, 5.0f), Points.ToArray());

                image.Save("result.png");
            }
        }
    }
}

The original input:

The resultant image: