Problems to understand DXGI DirectX 11 Desktop Duplication to get a Buffer or Array

Question

I want to understand DXGI Desktop Duplication. I have read a lot and this is the code I copied from parts of the DesktopDuplication sample on the Microsoft Website. My plan is to get the Buffer or Array from the DesktopImage because I want to make a new Texture for an other program. I hope somebody can explain me what I can do to get it.

void DesktopDublication::GetFrame(_Out_ FRAME_DATA* Data, _Out_ bool* Timeout)
{
    IDXGIResource* DesktopResource = nullptr;
    DXGI_OUTDUPL_FRAME_INFO FrameInfo;

    // Get new frame
    HRESULT hr = m_DeskDupl->AcquireNextFrame(500, &FrameInfo, &DesktopResource);
    if (hr == DXGI_ERROR_WAIT_TIMEOUT)
    {
        *Timeout = true;

    }
    *Timeout = false;

    if (FAILED(hr))
    {

    }

    // If still holding old frame, destroy it
    if (m_AcquiredDesktopImage)
    {
        m_AcquiredDesktopImage->Release();
        m_AcquiredDesktopImage = nullptr;
    }

    // QI for IDXGIResource
    hr = DesktopResource->QueryInterface(__uuidof(ID3D11Texture2D), reinterpret_cast<void **>(&m_AcquiredDesktopImage));
    DesktopResource->Release();
    DesktopResource = nullptr;
    if (FAILED(hr))
    {

    }

    // Get metadata
    if (FrameInfo.TotalMetadataBufferSize)
    {
        // Old buffer too small
        if (FrameInfo.TotalMetadataBufferSize > m_MetaDataSize)
        {
            if (m_MetaDataBuffer)
            {
                delete[] m_MetaDataBuffer;
                m_MetaDataBuffer = nullptr;
            }
            m_MetaDataBuffer = new (std::nothrow) BYTE[FrameInfo.TotalMetadataBufferSize];
            if (!m_MetaDataBuffer)
            {
                m_MetaDataSize = 0;
                Data->MoveCount = 0;
                Data->DirtyCount = 0;

            }
            m_MetaDataSize = FrameInfo.TotalMetadataBufferSize;
        }

        UINT BufSize = FrameInfo.TotalMetadataBufferSize;

        // Get move rectangles
        hr = m_DeskDupl->GetFrameMoveRects(BufSize, reinterpret_cast<DXGI_OUTDUPL_MOVE_RECT*>(m_MetaDataBuffer), &BufSize);
        if (FAILED(hr))
        {
            Data->MoveCount = 0;
            Data->DirtyCount = 0;

        }
        Data->MoveCount = BufSize / sizeof(DXGI_OUTDUPL_MOVE_RECT);

        BYTE* DirtyRects = m_MetaDataBuffer + BufSize;
        BufSize = FrameInfo.TotalMetadataBufferSize - BufSize;

        // Get dirty rectangles
        hr = m_DeskDupl->GetFrameDirtyRects(BufSize, reinterpret_cast<RECT*>(DirtyRects), &BufSize);
        if (FAILED(hr))
        {
            Data->MoveCount = 0;
            Data->DirtyCount = 0;

        }
        Data->DirtyCount = BufSize / sizeof(RECT);

        Data->MetaData = m_MetaDataBuffer;
    }

    Data->Frame = m_AcquiredDesktopImage;
    Data->FrameInfo = FrameInfo;
}

Answer 1

If I'm understanding you correctly, you want to get the current desktop image, duplicate it into a private texture, and then render that private texture onto your window. I would start by reading up on Direct3D 11 and learning how to render a scene, as you will need D3D to do anything with the texture object you get from DXGI. This, this, and this can get you started on D3D11. I would also spend some time reading through the source of the sample you copied your code from, as it completely explains how to do this. Here is the link to the full source code for that sample.

To actually get the texture data and render it out, you need to do the following:

1). Create a D3D11 Device object and a Device Context.

2). Write and compile a Vertex and Pixel shader for the graphics card, then load them into your application.

3). Create an Input Layout object and set it to the device.

4). Initialize the required Blend, Depth-Stencil, and Rasterizer states for the device.

5). Create a Texture object and a Shader Resource View object.

6). Acquire the Desktop Duplication texture using the above code.

7). Use CopyResource to copy the data into your texture.

8). Render that texture to the screen.

This will capture all data displayed on one of the desktops to your texture. It does not do processing on the dirty rects of the desktop. It does not do processing on moved regions. This is bare bones 'capture the desktop and display it elsewhere' code.

If you want to get more in depth, read the linked resources and study the sample code, as the sample basically does what you're asking for.

Answer 2

Since tacking this onto my last answer didn't feel quite right, I decided to create a second.

If you want to read the desktop data to a file, you need a D3D11 Device object, a texture object with the D3D11_USAGE_STAGING flag set, and a method of converting the RGBA pixel data of the desktop texture to whatever it is you want. The basic procedure is a simplified version of the one in my original answer:

1). Create a D3D11 Device object and a Device Context.

2). Create a Staging Texture with the same format as the Desktop Texture.

3). Use CopyResource to copy the Desktop Texture into your Staging Texture.

4). Use ID3D11DeviceContext::Map() to get a pointer to the data contained in the Staging Texture.

Make sure you know how Map works and make sure you can write out image files from a single binary stream. There may also be padding in the image buffer, so be aware you may also need to filter that out. Additionally, make sure you Unmap the buffer instead of calling free, as the buffer given to you almost certainly does not belong to the CRT.