Resizing a DXGI Resource or Texture2D in SharpDX

Question

I want to resize a screen captured using the Desktop Duplication API in SharpDX. I am using the Screen Capture sample code from the SharpDX Samples repository, relevant port

Answer 1

If you are fine resizing to a power of two from the screen, you can do it by:

• Create a smaller texture with RenderTarget/ShaderResource usage, and options GenerateMipMaps, same size of screen, mipcount > 1 (2 for having size /2, 3 for having /4...etc.).
• Copy the first mipmap of the screen texture to the smaller texture
• DeviceContext.GenerateMipMaps on the smaller texture
• Copy the selected mimap of the smaller texture (1: /2, 2: /4...etc.) to the staging texture (that should also be declared smaller, i.e. same size as the mipmap that is going to be used)

A quick hack on the original code to generate a /2 texture would be like this:

    [STAThread]
    private static void Main()
    {
        // # of graphics card adapter
        const int numAdapter = 0;

        // # of output device (i.e. monitor)
        const int numOutput = 0;

        const string outputFileName = "ScreenCapture.bmp";

        // Create DXGI Factory1
        var factory = new Factory1();
        var adapter = factory.GetAdapter1(numAdapter);

        // Create device from Adapter
        var device = new Device(adapter);

        // Get DXGI.Output
        var output = adapter.GetOutput(numOutput);
        var output1 = output.QueryInterface();

        // Width/Height of desktop to capture
        int width = output.Description.DesktopBounds.Width;
        int height = output.Description.DesktopBounds.Height;

        // Create Staging texture CPU-accessible
        var textureDesc = new Texture2DDescription
                              {
                                  CpuAccessFlags = CpuAccessFlags.Read,
                                  BindFlags = BindFlags.None,
                                  Format = Format.B8G8R8A8_UNorm,
                                  Width = width/2,
                                  Height = height/2,
                                  OptionFlags = ResourceOptionFlags.None,
                                  MipLevels = 1,
                                  ArraySize = 1,
                                  SampleDescription = { Count = 1, Quality = 0 },
                                  Usage = ResourceUsage.Staging
                              };
        var stagingTexture = new Texture2D(device, textureDesc);

        // Create Staging texture CPU-accessible
        var smallerTextureDesc = new Texture2DDescription
        {
            CpuAccessFlags = CpuAccessFlags.None,
            BindFlags = BindFlags.RenderTarget | BindFlags.ShaderResource,
            Format = Format.B8G8R8A8_UNorm,
            Width = width,
            Height = height,
            OptionFlags = ResourceOptionFlags.GenerateMipMaps,
            MipLevels = 4,
            ArraySize = 1,
            SampleDescription = { Count = 1, Quality = 0 },
            Usage = ResourceUsage.Default
        };
        var smallerTexture = new Texture2D(device, smallerTextureDesc);
        var smallerTextureView = new ShaderResourceView(device, smallerTexture);

        // Duplicate the output
        var duplicatedOutput = output1.DuplicateOutput(device);

        bool captureDone = false;
        for (int i = 0; !captureDone; i++)
        {
            try
            {
                SharpDX.DXGI.Resource screenResource;
                OutputDuplicateFrameInformation duplicateFrameInformation;

                // Try to get duplicated frame within given time
                duplicatedOutput.AcquireNextFrame(10000, out duplicateFrameInformation, out screenResource);

                if (i > 0)
                {
                    // copy resource into memory that can be accessed by the CPU
                    using (var screenTexture2D = screenResource.QueryInterface())
                        device.ImmediateContext.CopySubresourceRegion(screenTexture2D, 0, null, smallerTexture, 0);

                    // Generates the mipmap of the screen
                    device.ImmediateContext.GenerateMips(smallerTextureView);

                    // Copy the mipmap 1 of smallerTexture (size/2) to the staging texture
                    device.ImmediateContext.CopySubresourceRegion(smallerTexture, 1, null, stagingTexture, 0);

                    // Get the desktop capture texture
                    var mapSource = device.ImmediateContext.MapSubresource(stagingTexture, 0, MapMode.Read, MapFlags.None);

                    // Create Drawing.Bitmap
                    var bitmap = new System.Drawing.Bitmap(width/2, height/2, PixelFormat.Format32bppArgb);
                    var boundsRect = new System.Drawing.Rectangle(0, 0, width/2, height/2);

                    // Copy pixels from screen capture Texture to GDI bitmap
                    var mapDest = bitmap.LockBits(boundsRect, ImageLockMode.WriteOnly, bitmap.PixelFormat);
                    var sourcePtr = mapSource.DataPointer;
                    var destPtr = mapDest.Scan0;
                    for (int y = 0; y < height/2; y++)
                    {
                        // Copy a single line 
                        Utilities.CopyMemory(destPtr, sourcePtr, width/2 * 4);

                        // Advance pointers
                        sourcePtr = IntPtr.Add(sourcePtr, mapSource.RowPitch);
                        destPtr = IntPtr.Add(destPtr, mapDest.Stride);
                    }

                    // Release source and dest locks
                    bitmap.UnlockBits(mapDest);
                    device.ImmediateContext.UnmapSubresource(stagingTexture, 0);

                    // Save the output
                    bitmap.Save(outputFileName);

                    // Capture done
                    captureDone = true;
                }

                screenResource.Dispose();
                duplicatedOutput.ReleaseFrame();

            }
            catch (SharpDXException e)
            {
                if (e.ResultCode.Code != SharpDX.DXGI.ResultCode.WaitTimeout.Result.Code)
                {
                    throw e;
                }
            }
        }

        // Display the texture using system associated viewer
        System.Diagnostics.Process.Start(Path.GetFullPath(Path.Combine(Environment.CurrentDirectory, outputFileName)));

        // TODO: We should cleanp up all allocated COM objects here
    }