How to draw the points( with floating value) over a bitmap picture?

Question

I captured a video and took out a frame of that, converted it to Bitmap and now I can show it on picture box.

I have some float points which is the return values of GoodFeaturesToTrack() function from image class.

Now I want to draw/show those points/marks on different Xi,Yi over my picture;

How is it possible to do it? which command I have to use?

Answer 1

You could use builtin OpenCV functions to render around the feature points found, before you convert your image to a normal bitmap. This is also going to be much faster, as the image class will work with the raw memory rather than issue graphics calls.

Here's an (incomplete) example to illustrate the point. Note: you might need to adjust the calls to the CV signatures declared by your wrapper:

    private int maxPointCount = 16;
    private CvPoint2D32f[] points = new CvPoint2D32f[maxPointCount];
    private CvImage grayImage = new CvImage(size, CvColorDepth.U8, CvChannels.One);
    private CvImage eigenValues = new CvImage(size, CvColorDepth.F32, CvChannels.One);
    private CvImage tempImage = new CvImage(size, CvColorDepth.F32, CvChannels.One);

    public int FeatureRadius { get; set; }

    private CvScalar featureColor; 
    public Color FeatureColor
    {
        get
        {
            return Color.FromArgb((byte)featureColor.Value2, (byte)featureColor.Value1, (byte)featureColor.Value0);
        }
        set
        {
            featureColor.Value0 = value.B;
            featureColor.Value1 = value.G;
            featureColor.Value2 = value.R;
        }
    }

    public void Process(CvImage input, CvImage output)
    {
        CV.ConvertImage(input, grayImage);
        CV.GoodFeaturesToTrack(grayImage, eigenValues, tempImage, points, ref maxPointCount, 0.01, 10, IntPtr.Zero, 3, 0, 0.04);
        CV.Copy(input, output);

        // This draws a circle around the feature points found
        for (int i = 0; i < pointCount; i++)
            CV.Circle(output, new CvPoint((int)points[i].X, (int)points[i].Y), FeatureRadius, featureColor);
    }