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Thread: OpenGL screenShot a game

  1. #1
    Newbie Newbie
    Join Date
    Apr 2013

    OpenGL screenShot a game

    Hello everybody,

    I need some help!

    I have this code in c#:

    Code :
    // Creates a 1.0-compatible GraphicsContext with GraphicsMode.Default
            GameWindow window = new GameWindow();
            // Creates a 3.0-compatible GraphicsContext with 32bpp color, 24bpp depth
            // 8bpp stencil and 4x anti-aliasing.
            GLControl control = new GLControl(new GraphicsMode(32, 24, 8, 4), 3, 0, 0);
            public Bitmap GrabScreenshot()
                if (GraphicsContext.CurrentContext == null)
                    throw new GraphicsContextMissingException();
                Bitmap bmp = new Bitmap(this.ClientSize.Width, this.ClientSize.Height);
                System.Drawing.Imaging.BitmapData data =
                    bmp.LockBits(this.ClientRectangle, System.Drawing.Imaging.ImageLockMode.WriteOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
                GL.ReadPixels(0, 0, this.ClientSize.Width, this.ClientSize.Height, PixelFormat.Bgr, PixelType.UnsignedByte, data.Scan0);
                return bmp;
            public void framebuffer()
                const int FboWidth = 512;
                const int FboHeight = 512;
                uint FboHandle;
                uint ColorTexture;
                uint DepthRenderbuffer;
                // Create Color Texture
                GL.GenTextures(1, out ColorTexture);
                GL.BindTexture(TextureTarget.Texture2D, ColorTexture);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Nearest);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Nearest);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)TextureWrapMode.Clamp);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)TextureWrapMode.Clamp);
                GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba8, FboWidth, FboHeight, 0, PixelFormat.Rgba, PixelType.UnsignedByte, IntPtr.Zero);
                // test for GL Error here (might be unsupported format)
                GL.BindTexture(TextureTarget.Texture2D, 0); // prevent feedback, reading and writing to the same image is a bad idea
                // Create Depth Renderbuffer
                GL.Ext.GenRenderbuffers(1, out DepthRenderbuffer);
                GL.Ext.BindRenderbuffer(RenderbufferTarget.RenderbufferExt, DepthRenderbuffer);
                GL.Ext.RenderbufferStorage(RenderbufferTarget.RenderbufferExt, (RenderbufferStorage)All.DepthComponent32, FboWidth, FboHeight);
                // test for GL Error here (might be unsupported format)
                // Create a FBO and attach the textures
                GL.Ext.GenFramebuffers(1, out FboHandle);
                GL.Ext.BindFramebuffer(FramebufferTarget.FramebufferExt, FboHandle);
                GL.Ext.FramebufferTexture2D(FramebufferTarget.FramebufferExt, FramebufferAttachment.ColorAttachment0Ext, TextureTarget.Texture2D, ColorTexture, 0);
                GL.Ext.FramebufferRenderbuffer(FramebufferTarget.FramebufferExt, FramebufferAttachment.DepthAttachmentExt, RenderbufferTarget.RenderbufferExt, DepthRenderbuffer);
                // now GL.Ext.CheckFramebufferStatus( FramebufferTarget.FramebufferExt ) can be called, check the end of this page for a snippet.
                // since there's only 1 Color buffer attached this is not explicitly required
                GL.PushAttrib(AttribMask.ViewportBit); // stores GL.Viewport() parameters
                GL.Viewport(0, 0, FboWidth, FboHeight);
                // render whatever your heart desires, when done ...
                GL.PopAttrib(); // restores GL.Viewport() parameters
                GL.Ext.BindFramebuffer(FramebufferTarget.FramebufferExt, 0); // return to visible framebuffer
                DrawBuffersEnum[] bufs = new DrawBuffersEnum[2] { (DrawBuffersEnum)FramebufferAttachment.ColorAttachment0Ext, (DrawBuffersEnum)FramebufferAttachment.ColorAttachment1Ext }; // fugly, will be addressed in 0.9.2
                GL.DrawBuffers(bufs.Length, bufs);
            private void button1_Click(object sender, EventArgs e)
                pictureBox1.Image = GrabScreenshot();

    But the screenshot still black, someone can help me ?

    thanks! This is from OpenTK librarie!

  2. #2
    Newbie Newbie
    Join Date
    Apr 2013
    help me please!

  3. #3
    Senior Member OpenGL Pro
    Join Date
    Jan 2012
    I don't program in C# but it might be a problem with which render buffer is bound when you grab the data.

  4. #4
    Newbie Newbie
    Join Date
    Apr 2013
    i try inject this on counter strike, but give me an error, null exepcion

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