Drawing on image with Aforge.net Not working

Question

I'm trying to draw on an image

Graphics g = Graphics.FromImage(BWImage);
        Pen red = new Pen(Color.Red, 2);
        foreach (Blob blob in blobs)
        {
            List<IntPoint> leftPoints, rightPoints, edgePoints = new List<IntPoint>();

            // get blob's edge points
            blobCounter.GetBlobsLeftAndRightEdges(blob,
                 out leftPoints, out rightPoints);

            edgePoints.AddRange(leftPoints);
            edgePoints.AddRange(rightPoints);

            // blob's convex hull
            List<IntPoint> hull = hullFinder.FindHull(edgePoints);

            g.DrawPolygon(red, ToPointsArray(hull));

        }

I get frames from a webcam, and for each frame I do some processing then do that code, but it didn't work, I tried to debug it, I found that the line

Graphics g = Graphics.FromImage(BWImage);

It keeps executing forever without executing any line after it!
Any help please? Thanks.

Here is my code

 private void video_NewFrame(object sender, NewFrameEventArgs eventArgs)
    {
        Bitmap bitmap = (Bitmap)eventArgs.Frame.Clone();

        ProcessImage(bitmap);
    }

and the ProcessImage method:

#region Skin Detection
        YCbCrFiltering YCbCrFilter = new YCbCrFiltering();

        YCbCrFilter.Y = new Range(0, 1);
        YCbCrFilter.Cb = new Range(-0.1862745098039216f, 0.0294117647058824f);
        YCbCrFilter.Cr = new Range(0.0137254901960784f, 0.2254901960784314f);
        // apply the filter
        var YCbCrFilteredImage = YCbCrFilter.Apply(bitmap);

        #endregion

        #region GrayScale

        // create grayscale filter (BT709)
        Grayscale Gray_filter = new Grayscale(0.2125, 0.7154, 0.0721);
        // apply the filter
        Bitmap grayImage = Gray_filter.Apply(YCbCrFilteredImage);

        Threshold threshold = new Threshold(50);
        Bitmap BWImage = threshold.Apply(grayImage);

        #endregion

        #region Remove noise
        // create filter
        BlobsFiltering BlobsFilteringfilter = new BlobsFiltering();
        // configure filter
        BlobsFilteringfilter.CoupledSizeFiltering = true;
        BlobsFilteringfilter.MinWidth = 150;
        BlobsFilteringfilter.MinHeight = 150;
        BlobsFilteringfilter.MaxHeight = 600;
        BlobsFilteringfilter.MaxWidth = 600; 
        // apply the filter
        var BWImageFiltered = BlobsFilteringfilter.Apply(BWImage);
        #endregion


        #region Fill Holes
        FillHoles FillHolesfilter = new FillHoles();
        FillHolesfilter.MaxHoleHeight = 50;
        FillHolesfilter.MaxHoleWidth = 50;
        FillHolesfilter.CoupledSizeFiltering = false;
        var BWImageFilteredHoles = FillHolesfilter.Apply(BWImageFiltered);
        #endregion

        #region Contouring

        // process image with blob counter
        BlobCounter blobCounter = new BlobCounter();
        blobCounter.ProcessImage(BWImageFilteredHoles);
        Blob[] blobs = blobCounter.GetObjectsInformation();

        Graphics g = Graphics.FromImage(BWImageFilteredHoles);
        Pen red = new Pen(Color.Red, 2);
        // create convex hull searching algorithm
        GrahamConvexHull hullFinder = new GrahamConvexHull();
foreach (Blob blob in blobs)
        {
            List<IntPoint> AllEdgesPoints = new List<IntPoint>();
            List<IntPoint> leftPoints, rightPoints, edgePoints = new List<IntPoint>();

            // get blob's edge points
            blobCounter.GetBlobsLeftAndRightEdges(blob,
                 out leftPoints, out rightPoints);

            edgePoints.AddRange(leftPoints);
            edgePoints.AddRange(rightPoints);

            // blob's convex hull
            List<IntPoint> hull = hullFinder.FindHull(edgePoints);

            g.DrawPolygon(red, ToPointsArray(hull));
 g.Dispose();

        #endregion

        pictureBox1.Image = grayImage;
        pictureBox2.Image = BWImage;
    }

Answer 1

Is there an exception handler around this code that isn't shown? Graphics.FromImage() should be throwing an exception because you're passing an image with an indexed pixel format; Grayscale.Apply() returns an image with Format8bppIndexed, and BlobsFiltering.Apply() would preserve that.

Bottom line, you need to create a new Bitmap with the same size as BWImage, get your Graphics from that, paint BWImage onto the new image, then rectangle your blobs.