ID3D11DeviceContext渲染后的数据存储为BMP图片

void SaveBackBufferToFile(IDXGISwapChain1* pSwapChain, ID3D11Device* pDevice, ID3D11DeviceContext* pDeviceContext) {
    // 获取当前的渲染目标图像
    ID3D11Texture2D* pBackBuffer = nullptr;
    HRESULT hr = pSwapChain->GetBuffer(0, __uuidof(ID3D11Texture2D), (void**)&pBackBuffer);
    if (FAILED(hr))
    {
        // 错误处理
        return;
    }

    // 创建一个可用于读取的纹理
    D3D11_TEXTURE2D_DESC desc;
    pBackBuffer->GetDesc(&desc);

    D3D11_TEXTURE2D_DESC copyDesc = desc;
   copyDesc.Usage = D3D11_USAGE_STAGING;
   copyDesc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
   copyDesc.BindFlags = 0;

    D3D11_SUBRESOURCE_DATA subdata;
    RtlZeroMemory(&subdata, sizeof(D3D11_SUBRESOURCE_DATA));
    subdata.pSysMem = malloc(1280 * 720 * 4);

    ID3D11Texture2D* pStagingTexture = nullptr;
    hr = pDevice->CreateTexture2D(&copyDesc, NULL, &pStagingTexture);
    if (FAILED(hr)) 
    {
        // 错误处理
        pBackBuffer->Release();
        return;
    }

    // 复制图像数据到目标纹理
    pDeviceContext->CopyResource(pStagingTexture, pBackBuffer);

    // 读取图像数据到 CPU 内存
    D3D11_MAPPED_SUBRESOURCE mappedResource;
    hr = pDeviceContext->Map(pStagingTexture, 0, D3D11_MAP_READ, 0, &mappedResource);
    if (FAILED(hr)) {
        // 错误处理
        pStagingTexture->Release();
        pBackBuffer->Release();
        return;
    }

    // BMP 文件头和信息头
    BITMAPFILEHEADER bfh;
    BITMAPINFOHEADER bih;
    ZeroMemory(&bfh, sizeof(bfh));
    ZeroMemory(&bih, sizeof(bih));

    bfh.bfType = 0x4D42;  // "BM"
    bfh.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bfh.bfSize = bfh.bfOffBits + desc.Width * desc.Height * 4;

    bih.biSize = sizeof(BITMAPINFOHEADER);
    bih.biWidth = desc.Width;
    bih.biHeight = desc.Height;  // BMP 文件中的高度是负值表示从顶部到底部扫描
    bih.biPlanes = 1;
    bih.biBitCount = 32;  // 32位颜色深度
    bih.biCompression = BI_RGB;

    // 打开文件进行写入
    FILE* pFile = fopen("screenshot.bmp", "wb");
    if (pFile) {
        fwrite(&bfh, sizeof(BITMAPFILEHEADER), 1, pFile);
        fwrite(&bih, sizeof(BITMAPINFOHEADER), 1, pFile);
        fwrite(mappedResource.pData, desc.Width * desc.Height * 4, 1, pFile);
        fclose(pFile);
    }

    pDeviceContext->Unmap(pStagingTexture, 0);
    pStagingTexture->Release();
    pBackBuffer->Release();
}