How to create bitmap from Surface (SharpDX) - directx-11

Question

I am new to DirectX and trying to use SharpDX to capture a screen shot using the Desktop Duplication API.
I am wondering if there is any easy way to create bitmap that I can use in CPU (i.e. save on file, etc.)
I am using the following code the get the desktop screen shot:
var factory = new SharpDX.DXGI.Factory1();
var adapter = factory.Adapters1[0];
var output = adapter.Outputs[0];
var device = new SharpDX.Direct3D11.Device(SharpDX.Direct3D.DriverType.Hardware,
DeviceCreationFlags.BgraSupport |
DeviceCreationFlags.Debug);
var dev1 = device.QueryInterface<SharpDX.DXGI.Device1>();
var output1 = output.QueryInterface<Output1>();
var duplication = output1.DuplicateOutput(dev1);
OutputDuplicateFrameInformation frameInfo;
SharpDX.DXGI.Resource desktopResource;
duplication.AcquireNextFrame(50, out frameInfo, out desktopResource);
var desktopSurface = desktopResource.QueryInterface<Surface>();
can anyone please give me some idea on how can I create a bitmap object from the desktopSurface (DXGI.Surface instance)?

Answer 1

I've just completed this myself although I am not going to say much about this code!
public byte[] GetScreenData()
{
// We want to copy the texture from the back buffer so
// we don't hog it.
Texture2DDescription desc = BackBuffer.Description;
desc.CpuAccessFlags = CpuAccessFlags.Read;
desc.Usage = ResourceUsage.Staging;
desc.OptionFlags = ResourceOptionFlags.None;
desc.BindFlags = BindFlags.None;
byte[] data = null;
using (var texture = new Texture2D(DeviceDirect3D, desc))
{
DeviceContextDirect3D.CopyResource(BackBuffer, texture);
using (Surface surface = texture.QueryInterface<Surface>())
{
DataStream dataStream;
var map = surface.Map(SharpDX.DXGI.MapFlags.Read, out dataStream);
int lines = (int)(dataStream.Length / map.Pitch);
data = new byte[surface.Description.Width * surface.Description.Height * 4];
int dataCounter = 0;
// width of the surface - 4 bytes per pixel.
int actualWidth = surface.Description.Width * 4;
for (int y = 0; y < lines; y++)
{
for (int x = 0; x < map.Pitch; x++)
{
if (x < actualWidth)
{
data[dataCounter++] = dataStream.Read<byte>();
}
else
{
dataStream.Read<byte>();
}
}
}
dataStream.Dispose();
surface.Unmap();
}
}
return data;
}
This will get you a byte[] which can then be used to generate a bitmap.
The following is how I saved to a png Image.
using (var stream = await file.OpenAsync( Windows.Storage.FileAccessMode.ReadWrite ))
{
BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, stream);
double dpi = DisplayProperties.LogicalDpi;
encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight,
(uint)width, (uint)height, dpi, dpi, pixelData);
encoder.BitmapTransform.ScaledWidth = (uint)newWidth;
encoder.BitmapTransform.ScaledHeight = (uint)newHeight;
await encoder.FlushAsync();
waiter.Set();
}
I know this was answered a while ago, and maybe you figured it out by now :3 but if someone else gets stuck I hope this helps!

Answer 2

The MSDN page for the Desktop Duplication API tells us the format of the image:
DXGI provides a surface that contains a current desktop image through the new IDXGIOutputDuplication::AcquireNextFrame method. The format of the desktop image is always DXGI_FORMAT_B8G8R8A8_UNORM no matter what the current display mode is.
You can use the Surface.Map(MapFlags, out DataStream) method get access to the data on the CPU.
The code should look like* this:
DataStream dataStream;
desktopSurface.Map(MapFlags.Read, out dataStream);
for(int y = 0; y < surface.Description.Width; y++) {
for(int x = 0; x < surface.Description.Height; x++) {
// read DXGI_FORMAT_B8G8R8A8_UNORM pixel:
byte b = dataStream.Read<byte>();
byte g = dataStream.Read<byte>();
byte r = dataStream.Read<byte>();
byte a = dataStream.Read<byte>();
// color (r, g, b, a) and pixel position (x, y) are available
// TODO: write to bitmap or process otherwise
}
}
desktopSurface.Unmap();
*Disclaimer: I don't have a Windows 8 installation at hand, I'm only following the documentation. I hope this works :)