c++ Directx11 截屏并保存到文件

Question

我在将 texture2d 保存到文件时遇到问题，它总是给我黑色图像。 这是代码：

HRESULT hr = SwapChain->GetBuffer( 0, __uuidof( ID3D11Texture2D ), reinterpret_cast< void** >( &g_pSurface ) );
if( g_pSurface )
{
    ID3D11Texture2D* pNewTexture = NULL;

    D3D11_TEXTURE2D_DESC description;
    g_pSurface->GetDesc( &description );
    description.BindFlags = 0;
    description.CPUAccessFlags = D3D11_CPU_ACCESS_READ | D3D11_CPU_ACCESS_WRITE;
    description.Usage = D3D11_USAGE_STAGING;

    HRESULT hr = d3d11Device->CreateTexture2D( &description, NULL, &pNewTexture );
    if( pNewTexture )
    {
        d3d11DevCon->CopyResource( pNewTexture, g_pSurface );

        hr=D3DX11SaveTextureToFileA(d3d11DevCon, pNewTexture, D3DX11_IFF_BMP, "screen.bmp");
        return;
    }
}

我做错了什么？

Answer 1

首先，您需要明确检查所有返回 HRESULT 的函数的返回代码

HRESULT hr = SwapChain->GetBuffer( 0, __uuidof( ID3D11Texture2D ),
    reinterpret_cast< void** >( &g_pSurface ) );
if( SUCCEEDED(hr) )
{
...
    HRESULT hr = d3d11Device->CreateTexture2D( &description, NULL, &pNewTexture );
    if( SUCCEEDED(hr) )

一个可能的故障点是CopyResource，它返回 void，因此您无法在代码中检测到问题。相反，您需要启用 Direct3D DEBUG 设备并查找任何错误或警告消息。

特别是，如果您的交换链缓冲区是 MSAA 资源，则将无法获取任何数据。在进行复制之前，您必须明确使用 ResolveSubresource。反过来由于ResolveSubresource返回一个void，你需要在使用之前检查格式支持D3D11_FORMAT_SUPPORT_MULTISAMPLE_RESOLVE。这是 DirectX Tool Kit 中的 ScreenGrab 模块中的代码，用于执行此处理：

static HRESULT CaptureTexture( _In_ ID3D11DeviceContext* pContext,
                               _In_ ID3D11Resource* pSource,
                               _Inout_ D3D11_TEXTURE2D_DESC& desc,
                               _Inout_ ComPtr<ID3D11Texture2D>& pStaging )
{
    if ( !pContext || !pSource )
        return E_INVALIDARG;

    D3D11_RESOURCE_DIMENSION resType = D3D11_RESOURCE_DIMENSION_UNKNOWN;
    pSource->GetType( &resType );

    if ( resType != D3D11_RESOURCE_DIMENSION_TEXTURE2D )
        return HRESULT_FROM_WIN32( ERROR_NOT_SUPPORTED );

    ComPtr<ID3D11Texture2D> pTexture;
    HRESULT hr = pSource->QueryInterface( __uuidof(ID3D11Texture2D), reinterpret_cast<void**>( pTexture.GetAddressOf() ) );
    if ( FAILED(hr) )
        return hr;

    assert( pTexture );

    pTexture->GetDesc( &desc );

    ComPtr<ID3D11Device> d3dDevice;
    pContext->GetDevice( d3dDevice.GetAddressOf() );

    if ( desc.SampleDesc.Count > 1 )
    {
        // MSAA content must be resolved before being copied to a staging texture
        desc.SampleDesc.Count = 1;
        desc.SampleDesc.Quality = 0;

        ComPtr<ID3D11Texture2D> pTemp;
        hr = d3dDevice->CreateTexture2D( &desc, 0, pTemp.GetAddressOf() );
        if ( FAILED(hr) )
            return hr;

        assert( pTemp );

        DXGI_FORMAT fmt = EnsureNotTypeless( desc.Format );

        UINT support = 0;
        hr = d3dDevice->CheckFormatSupport( fmt, &support );
        if ( FAILED(hr) )
            return hr;

        if ( !(support & D3D11_FORMAT_SUPPORT_MULTISAMPLE_RESOLVE) )
            return E_FAIL;

        for( UINT item = 0; item < desc.ArraySize; ++item )
        {
            for( UINT level = 0; level < desc.MipLevels; ++level )
            {
                UINT index = D3D11CalcSubresource( level, item, desc.MipLevels );
                pContext->ResolveSubresource( pTemp.Get(), index, pSource, index, fmt );
            }
        }

        desc.BindFlags = 0;
        desc.MiscFlags &= D3D11_RESOURCE_MISC_TEXTURECUBE;
        desc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
        desc.Usage = D3D11_USAGE_STAGING;

        hr = d3dDevice->CreateTexture2D( &desc, 0, pStaging.GetAddressOf() );
        if ( FAILED(hr) )
            return hr;

        assert( pStaging );

        pContext->CopyResource( pStaging.Get(), pTemp.Get() );
    }
    else if ( (desc.Usage == D3D11_USAGE_STAGING) && (desc.CPUAccessFlags & D3D11_CPU_ACCESS_READ) )
    {
        // Handle case where the source is already a staging texture we can use directly
        pStaging = pTexture;
    }
    else
    {
        // Otherwise, create a staging texture from the non-MSAA source
        desc.BindFlags = 0;
        desc.MiscFlags &= D3D11_RESOURCE_MISC_TEXTURECUBE;
        desc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
        desc.Usage = D3D11_USAGE_STAGING;

        hr = d3dDevice->CreateTexture2D( &desc, 0, pStaging.GetAddressOf() );
        if ( FAILED(hr) )
            return hr;

        assert( pStaging );

        pContext->CopyResource( pStaging.Get(), pSource );
    }

事实上，您应该使用 DirectX Tool Kit 而不是旧的 D3DX11 库。所有版本的 D3DX 都已弃用，旧版 DirectX SDK 本身也是如此（请参阅MSDN）。有许多容易获得的replacements。

除了 MSAA 问题之外，您可能还会遇到D3DX11 选择 WIC 格式的问题。根据您的渲染目标格式和渲染，它可能会写出具有全 0 alpha 通道的图像，这可能会导致“空白”输出图像。 DirectX 工具包 ScreenGrab 模块使您能够显式指定输出格式，并且出于这个原因默认尝试使用非 alpha 输出文件格式。

不使用旧版D3DX11 的另一个原因：它从未针对 DXGI 1.1 格式进行更新，因此即使底层 WIC 容器文件格式支持，它也不支持写出 BGRA 格式资源，例如 DXGI_FORMAT_B8G8R8A8_UNORM 或 DXGI_FORMAT_B8G8R8A8_UNORM他们。如果上面代码中的渲染目标是 DXGI_FORMAT_B8G8R8A8_UNORM 而不是 DXGI_FORMAT_R8G8B8A8_UNORM，那么 D3DX11 将失败，而 ScreenGrab 将正常工作。

我有没有提到 D3DX11 太老了，自 2009 年以来就没有对其进行过任何修复？

以下是 ScreenGrab 的一些示例用法：

ComPtr<ID3D11Texture2D> backBufferTex;
hr = swapChain->GetBuffer( 0, __uuidof( ID3D11Texture2D ), ( LPVOID* )&backBufferTex);
if ( SUCCEEDED(hr) )
{
    // Write out the render target as a PNG
    hr = SaveWICTextureToFile( context.Get(), backBufferTex.Get(), GUID_ContainerFormatPng, L"SCREENSHOT.PNG");

    // Write out the render target as JPG
    hr = SaveWICTextureToFile( context.Get(), backBufferTex.Get(), GUID_ContainerFormatJpeg, L"SCREENSHOT.JPG" );

    // Write out the render target as BMP
    hr = SaveWICTextureToFile( context.Get(), backBufferTex.Get(), GUID_ContainerFormatBmp, L"SCREENSHOT.BMP" );

    // Write out the render target as BMP and explicitly use a 16-bit format
    hr = SaveWICTextureToFile( context.Get(), backBufferTex.Get(), GUID_ContainerFormatBmp, L"SCREENSHOT.BMP", &GUID_WICPixelFormat16bppBGR565 );

    // Write out the render target as a TIF
    hr = SaveWICTextureToFile( context.Get(), backBufferTex.Get(), GUID_ContainerFormatTiff, L"SCREENSHOT.TIF" );

    // Write out the render target as a TIF with explicit WIC codec properties
    hr = SaveWICTextureToFile( context.Get(), backBufferTex.Get(), GUID_ContainerFormatTiff, L"SCREENSHOT.TIF", nullptr,
                                [&](IPropertyBag2* props)
                                {
                                    PROPBAG2 options[2] = { 0, 0 };
                                    options[0].pstrName = L"CompressionQuality";
                                    options[1].pstrName = L"TiffCompressionMethod";

                                    VARIANT varValues[2];
                                    varValues[0].vt = VT_R4;
                                    varValues[0].fltVal = 0.75f;

                                    varValues[1].vt = VT_UI1;
                                    varValues[1].bVal = WICTiffCompressionNone;

                                    (void)props->Write( 2, options, varValues ); 
                                });

    // Write out the render target as a DDS
    hr = SaveDDSTextureToFile( context.Get(), backBufferTex.Get(), L"SCREENSHOT.DDS" );
}

Answer 2

在设置所有值之前，您的描述已声明但未初始化为任何内容。它的MiscFlags 成员中可能有垃圾，会破坏您的创作。尝试设置description.MiscFlags = 0; 或先将整个描述清零。如果这样做不行，这里有一个从我当前可用的库中提取的代码示例：

试试这个：

HRESULT hr;

ID3D11Resource* pSurface = nullptr;
m_pRenderTargetView->GetResource(&pSurface);

if (pSurface)
{
    D3D11_TEXTURE2D_DESC desc;
    ZeroMemory(&desc, sizeof(desc));
    desc.ArraySize = 1;
    desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    desc.Width = clientWidth;
    desc.Height = clientHeight;
    desc.MipLevels = 1;
    desc.SampleDesc.Count = 1;
    desc.SampleDesc.Quality = 0;
    desc.BindFlags = 0;
    desc.CPUAccessFlags = 0;
    desc.Usage = D3D11_USAGE_DEFAULT;

    ID3D11Texture2D* pTexture = nullptr;
    hr = m_pDevice->CreateTexture2D(&desc, nullptr, &pTexture);
    if (pTexture)
    {
        m_pContext->CopyResource(pTexture, pSurface);
        hr = D3DX11SaveTextureToFileA(m_pContext, pTexture, D3DX11_IFF_PNG, "ss.png");
        pTexture->Release();
    }
    pSurface->Release();
}

Answer 3

要写入 MSAA 缓冲区（交换链中的后备缓冲区），需要使用“ResolveSubresource”而不是“CopyResource”。

这是一个简单的代码段：

          D3D11_TEXTURE2D_DESC desc;
          HRESULT hr = S_OK;
          ID3D11Resource* pSurface = nullptr;

          // get pointer to back-texture from the swap chain referred from the pointer IDXGISwapChain* g_pswapChain
          hr=g_pswapChain->GetBuffer(0, __uuidof(ID3D11Texture2D), reinterpret_cast<void**>(&pSurface));
          if (FAILED(hr) || pSurface==nullptr)
          {
             // Throw Error  
      
          }
        
          D3D11_TEXTURE2D_DESC desc;
          ZeroMemory(&desc, sizeof(desc));
          desc.ArraySize = 1;
          desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
          desc.Width = 640; // i specified hard-coded the window size 640x480 in CreateWindowA
           desc.Height = 480;
           desc.MipLevels = 1;
           desc.SampleDesc.Count = 1;
           desc.SampleDesc.Quality = 0;
           desc.BindFlags = 0;
           desc.CPUAccessFlags = 0;  // data directly will be copied from GPU to a file
          desc.Usage = D3D11_USAGE_DEFAULT;

          ID3D11Texture2D* pTexture = nullptr;

          // g_pdevice is pointer to device ID3D11Device
          hr = g_pdevice->CreateTexture2D(&desc, nullptr, &pTexture);
          if (pTexture)
          {
                  // instead of CopyResource(pTexture, pSurface), g_pd3dContext pointer to context ID3D11DeviceContext
                  g_pd3dContext->ResolveSubresource(pTexture, 0, pSurface, 0, DXGI_FORMAT_R8G8B8A8_UNORM);

                  // save rendered image as bmp-file
                  hr = D3DX11SaveTextureToFileA(g_pd3dContext, pTexture, D3DX11_IFF_BMP, "test.bmp");
                  pTexture->Release();
              }
              pSurface->Release();