OpenCV webcam frames to OpenGL texture

Question

I am working on C# and using OpenTK(OpenGL wrapper) and EmguCV(OpenCV wrapper).

What I want to do is easy to understand: Grab the webcam video stream and put it on a GLControl.

1. I have a static class called Capturer which has a method that captures a frame and returns it as a cv::Mat wrapped object:

   internal static void Initialize()
   {
       cap = new VideoCapture(1);
       cap.SetCaptureProperty(Emgu.CV.CvEnum.CapProp.Fps, 25);
       cap.SetCaptureProperty(Emgu.CV.CvEnum.CapProp.FrameWidth, 1920);
       cap.SetCaptureProperty(Emgu.CV.CvEnum.CapProp.FrameHeight, 1080);
   }
   
   internal static Mat GetCurrentFrame()
   {
       mat = cap.QueryFrame();
       if (!mat.IsEmpty)
       {
           return mat;
       }
       return null;
   }
   

2. Now in my GLControl Load event I initialize the capturer and OpenGL:

       Capturer.Initialize();
   
       GL.ClearColor(Color.Blue);
       GL.Enable(EnableCap.Texture2D);
   
       GL.Viewport(-glControl1.Width, -glControl1.Height, glControl1.Width * 2, glControl1.Height * 2);
   

3. And finally, in the GLControl Paint event:

       GL.Clear(ClearBufferMask.ColorBufferBit);
   
       GL.MatrixMode(MatrixMode.Projection);
       GL.LoadIdentity();
   
       Mat m = Capturer.GetCurrentFrame();
       if (m != null)
       {
           GL.GenTextures(1, out textureId);
           GL.BindTexture(TextureTarget.Texture2D, this.textureId);
   
           GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (float)TextureMinFilter.Nearest);
           GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (float)TextureMagFilter.Linear);
   
           GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (float)TextureWrapMode.Clamp);
           GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (float)TextureWrapMode.Clamp);
   
           GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgb, 1920, 1080, 0, OpenTK.Graphics.OpenGL.PixelFormat.Bgr, PixelType.UnsignedByte, m.DataPointer);
       }
       m.Dispose();
   
       glControl1.SwapBuffers();
       glControl1.Invalidate();
   

This is showing a full Blue screen. I think the error is on m.DataPointer.

(I have tried rendering the frames with Bitmap using the property m.Bitmapand it works but the performance is so bad.)

Answer 1

Drawing a rectangle bounding the GLControl solved it:

            GL.Begin(PrimitiveType.Quads);
                GL.TexCoord2(0, 0); GL.Vertex2(0, 0);
                GL.TexCoord2(0, 1); GL.Vertex2(0, 1);
                GL.TexCoord2(1, 1); GL.Vertex2(1, 1);
                GL.TexCoord2(1, 0); GL.Vertex2(1, 0);
            GL.End();
            m.Dispose();

Be sure to dispose the object after drawing the frame so you will not run out of memory.