在使用aforge blob计数器检测矩形之后如何提取blob

`// Process image private void ProcessImage（Bitmap bitmap）{// lock image BitmapData bitmapData = bitmap.LockBits（new Rectangle（0,0，bitmap.Width，bitmap.Height），ImageLockMode.ReadWrite，bitmap.PixelFormat）;

// step 2 - locating objects
        BlobCounter blobCounter = new BlobCounter();
        blobCounter.FilterBlobs = true;
        blobCounter.MinHeight = 5;
        blobCounter.MinWidth = 5;

        blobCounter.ObjectsOrder = ObjectsOrder.Size;
        blobCounter.ProcessImage(bitmapData);
        Blob[] blobs = blobCounter.GetObjectsInformation();
        bitmap.UnlockBits(bitmapData);

        // step 3 - check objects' type and highlight
        SimpleShapeChecker shapeChecker = new SimpleShapeChecker();

        Graphics g = Graphics.FromImage(bitmap);
        Pen redPen = new Pen(Color.Red, 2);       // quadrilateral

        for (int i = 0, n = blobs.Length; i < n; i++)
        {
            List<IntPoint> edgePoints = blobCounter.GetBlobsEdgePoints(blobs[i]);

            List<IntPoint> corners;
            // use the shape checker to extract the corner points
            if (shapeChecker.IsQuadrilateral(edgePoints,out corners ))
            {
                // only do things if the corners form a rectangle
                if (shapeChecker.CheckPolygonSubType(corners) == PolygonSubType.Rectangle)
                {

                    g.DrawPolygon(redPen, ToPointsArray(corners));

                }
            }
        }


        redPen.Dispose();
        g.Dispose();
        // put new image to clipboard
        Clipboard.SetDataObject(bitmap);
        // and to picture box
        pictureBox1.Image = bitmap;
       }


    }`In [this link][0] array of rectangles was detected. Now, my question is how do I extract the rectangle from the image. My scenario is I detect the rectangular License plate of a car (colored image converted to binary  ) in the image and draw with red the location of the plate.

现在我想从图像中提取红色绘制的板 . 我怎么做 .

由于我的图像是二值图像，我已应用扩张来获得正确的LP候选，所有候选在图像中被成功识别，但我无法使用 ExtractBiggestBlob 方法提取它们 .

请帮忙 . 提前致谢 .