# DX11 Getting bitmap from multisampled backbuffer

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Hi Everyone,

In my desktop application (using SlimDX & DX11 ) I need to make a snapshot of a rendered window. I use the following code to save the bitmap of the current back buffer:

            var context = device.ImmediateContext;
var srcTex = renderTarget.Resource as Texture2D;
var desc = srcTex.Description;
desc.BindFlags = BindFlags.None;
desc.Usage = ResourceUsage.Staging;
desc.SampleDescription = new SampleDescription(1, 0);
Texture2D staging = new Texture2D(device, desc);
context.CopyResource(srcTex, staging);
Texture2D.ToFile(context, staging, ImageFileFormat.Png, "c:/Temp/Screenshot.png");


This code works fine, if my renderTarget is not multisampled. If the renderTarget is multisampled ( as needed for anti-aliasing) I got blank image. Does anybody know a way to get a bitmap snapshot from a multisampled render target?

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You need to use ResolveSubresource first.

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Thank you very much for the quick response. It solves the problem completely. Just for people who might be encounter the same problem, my code to get a bitmap from current back-buffer looks as following:

        public Bitmap GetBitmap() {
var ctx = device.ImmediateContext;
var srcTex = renderTarget.Resource as Texture2D;

var desc = srcTex.Description;
desc.BindFlags = BindFlags.None;
desc.Usage = ResourceUsage.Staging;
desc.SampleDescription = new SampleDescription(1, 0);
Texture2D staging = new Texture2D(device, desc);

desc.Usage = ResourceUsage.Default;
desc.CpuAccessFlags = CpuAccessFlags.None;
Texture2D resolved = new Texture2D(device, desc);

ctx.ResolveSubresource(srcTex, 0, resolved, 0, desc.Format);
ctx.CopyResource(resolved, staging);

using (Surface surface = staging.AsSurface()) {
var rect = surface.Map(SlimDX.DXGI.MapFlags.Read);
Bitmap bm = new Bitmap(desc.Width, desc.Height,
rect.Pitch, PixelFormat.Format32bppArgb, rect.Data.DataPointer);
surface.Unmap();
resolved.Dispose();
staging.Dispose();
return bm;
}
}

Edited by jamesxli

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