Question

I am using Aforge to run edge detection on an image, how would I get the x,y for the detected edge(s) points? Other than the obvious way of looping through the image bitmaps.

This is the code from the Aforge samples, but how can I get the edge points?

    // On Filters->Sobel edge detector
            private void sobelEdgesFiltersItem_Click( object sender, System.EventArgs e )
            {
                // save original image
                Bitmap originalImage = sourceImage;
                // get grayscale image
                sourceImage = Grayscale.CommonAlgorithms.RMY.Apply( sourceImage );
                // apply edge filter
                ApplyFilter( new SobelEdgeDetector( ) );
                // delete grayscale image and restore original
                sourceImage.Dispose( );
                sourceImage = originalImage;

// this is the part where the source image is now edge detected. How to get the x,y for //each point of the edge? 

                sobelEdgesFiltersItem.Checked = true;
            }

Answer 1

The filters are merely what the name suggests: Filters (Image -> Process -> NewImage)

I don’t know, if there is something similar for edges, but AForge has a corner detector. My sample loads an image, runs the corner detector and displays little red boxes around every corner. (You’ll need a PictureBox control named “pictureBox”).

    public void DetectCorners()
    {
        // Load image and create everything you need for drawing
        Bitmap image = new Bitmap(@"myimage.jpg");
        Graphics graphics = Graphics.FromImage(image);
        SolidBrush brush = new SolidBrush(Color.Red);
        Pen pen = new Pen(brush);

        // Create corner detector and have it process the image
        MoravecCornersDetector mcd = new MoravecCornersDetector();
        List<IntPoint> corners = mcd.ProcessImage(image);

        // Visualization: Draw 3x3 boxes around the corners
        foreach (IntPoint corner in corners)
        {
            graphics.DrawRectangle(pen, corner.X - 1, corner.Y - 1, 3, 3);
        }

        // Display
        pictureBox.Image = image;
    }

It might not be exactly what you’re looking for, but maybe it helps.