Windows 10 下的高效抓屏方法

概述

  很多软件都需要屏幕捕捉功能，在软件中实现屏幕捕捉也不是难事，在微软Windows平台，有很多截屏的方法，例如：BitBlt、Mirror driver、 GDI hook、DirectX、DWM/Dxgi hook、Desktop Duplication与GetWindowDC 等方法，但大多效率不高，效率高的 Mirror driver技术只能用于XP等老系统，在Windows8 与Windows 10 上似乎已经失效，Windows8以后微软引入了一套新的接口，叫“Desktop Duplication API”，应用程序可以通过这套API访问桌面数据。
      Desktop Duplication API是通过Microsoft DirectX Graphics Infrastructure (DXGI)来提供桌面图像的，速度非常快。DXGI是通过GPU实现的，因此cpu占用率很低，性能非常高。 Duplication API获取到的桌面数据，不管显示模式如何设置，都永远是32位RGBA数据，这就给屏幕捕捉带来了很大的方便性，不再需要考虑各种显示模式的问题了。

要实现DXGI屏幕捕捉，基本流程如下：

1）创建D3DDevice；
2）通过一系列接口获取路径，获取到IDXGIOutputDuplication接口；
3）调用AcquireNextFrame，获取当前桌面数据，保存在IDXGIResource中；
4）把数据从GPU映射到内存中拷贝需要的数据到自己的buffer里。

其中，获取到IDXGIOutputDuplication接口，是通过如下路径：
IDXGIDevice --> IDXGIAdapter --> IDXGIOutput --> IDXGIOutput1 --> IDXGIOutputDuplication

真实实现DXGI屏幕捕捉的代码如下：

//
//DXGICapture.h
//

#include 
#include 

class VideoDXGICaptor
{
public:
    VideoDXGICaptor();
    ~VideoDXGICaptor();

public:
    BOOL Init();
    VOID Deinit();

public:
    virtual BOOL CaptureImage(RECT &rect, void *pData, INT &nLen);
    virtual BOOL CaptureImage(void *pData, INT &nLen);
    virtual BOOL ResetDevice();

private:
    BOOL  AttatchToThread(VOID);
    BOOL  QueryFrame(void *pImgData, INT &nImgSize);
    BOOL  QueryFrame(void *pImgData, INT &nImgSize, int z);

private:
    IDXGIResource *zhDesktopResource;
    DXGI_OUTDUPL_FRAME_INFO zFrameInfo;
    ID3D11Texture2D *zhAcquiredDesktopImage;
    IDXGISurface *zhStagingSurf;

private:
    BOOL                    m_bInit;
    int                     m_iWidth, m_iHeight;

    ID3D11Device           *m_hDevice;
    ID3D11DeviceContext    *m_hContext;

    IDXGIOutputDuplication *m_hDeskDupl;
    DXGI_OUTPUT_DESC        m_dxgiOutDesc;
};


//
//DXGICapture.cpp
//

#include "stdafx.h"
#include "DXGICaptor.h"
#include 
#include 

#pragma comment(lib, "d3d11.lib")
#pragma comment(lib, "dxgi.lib")

#define RESET_OBJECT(obj) { if(obj) obj->Release(); obj = NULL; }
static BOOL g_bAttach = FALSE;

VideoDXGICaptor::VideoDXGICaptor()
{
    m_bInit = FALSE;

    m_hDevice = NULL;
    m_hContext = NULL;
    m_hDeskDupl = NULL;

    ZeroMemory(&m_dxgiOutDesc, sizeof(m_dxgiOutDesc));
}
VideoDXGICaptor::~VideoDXGICaptor()
{
    Deinit();
}
BOOL VideoDXGICaptor::Init()
{
    HRESULT hr = S_OK;

    if (m_bInit)
    {
        return FALSE;
    }

    // Driver types supported
    D3D_DRIVER_TYPE DriverTypes[] =
    {
        D3D_DRIVER_TYPE_HARDWARE,
        D3D_DRIVER_TYPE_WARP,
        D3D_DRIVER_TYPE_REFERENCE,
    };
    UINT NumDriverTypes = ARRAYSIZE(DriverTypes);

    // Feature levels supported
    D3D_FEATURE_LEVEL FeatureLevels[] =
    {
        D3D_FEATURE_LEVEL_11_0,
        D3D_FEATURE_LEVEL_10_1,
        D3D_FEATURE_LEVEL_10_0,
        D3D_FEATURE_LEVEL_9_1
    };
    UINT NumFeatureLevels = ARRAYSIZE(FeatureLevels);

    D3D_FEATURE_LEVEL FeatureLevel;

    //
    // Create D3D device
    //
    for (UINT DriverTypeIndex = 0; DriverTypeIndex < NumDriverTypes; ++DriverTypeIndex)
    {
        hr = D3D11CreateDevice(NULL, DriverTypes[DriverTypeIndex], NULL, 0, FeatureLevels, NumFeatureLevels, D3D11_SDK_VERSION, &m_hDevice, &FeatureLevel, &m_hContext);
        if (SUCCEEDED(hr))
        {
            break;
        }
    }
    if (FAILED(hr))
    {
        return FALSE;
    }

    //
    // Get DXGI device
    //
    IDXGIDevice *hDxgiDevice = NULL;
    hr = m_hDevice->QueryInterface(__uuidof(IDXGIDevice), reinterpret_cast(&hDxgiDevice));
    if (FAILED(hr))
    {
        return FALSE;
    }

    //
    // Get DXGI adapter
    //
    IDXGIAdapter *hDxgiAdapter = NULL;
    hr = hDxgiDevice->GetParent(__uuidof(IDXGIAdapter), reinterpret_cast(&hDxgiAdapter));
    RESET_OBJECT(hDxgiDevice);
    if (FAILED(hr))
    {
        return FALSE;
    }

    //
    // Get output
    //
    INT nOutput = 0;
    IDXGIOutput *hDxgiOutput = NULL;
    hr = hDxgiAdapter->EnumOutputs(nOutput, &hDxgiOutput);
    RESET_OBJECT(hDxgiAdapter);
    if (FAILED(hr))
    {
        return FALSE;
    }

    //
    // get output description struct
    //
    hDxgiOutput->GetDesc(&m_dxgiOutDesc);
    
    //
    // QI for Output 1
    //
    IDXGIOutput1 *hDxgiOutput1 = NULL;
    hr = hDxgiOutput->QueryInterface(__uuidof(hDxgiOutput1), reinterpret_cast(&hDxgiOutput1));
    RESET_OBJECT(hDxgiOutput);
    if (FAILED(hr))
    {
        return FALSE;
    }

    //
    // Create desktop duplication
    //
    hr = hDxgiOutput1->DuplicateOutput(m_hDevice, &m_hDeskDupl);
    RESET_OBJECT(hDxgiOutput1);
    if (FAILED(hr))
    {
        return FALSE;
    }

    // 初始化成功
    m_bInit = TRUE;
    return TRUE;
// #else
    // 小于vs2012,此功能不能实现
    return FALSE;
// #endif
}
VOID VideoDXGICaptor::Deinit()
{
    if (!m_bInit)
    {
        return;
    }

    m_bInit = FALSE;

    if (m_hDeskDupl)
    {
        m_hDeskDupl->Release();
        m_hDeskDupl = NULL;
    }

    if (m_hDevice)
    {
        m_hDevice->Release();
        m_hDevice = NULL;
    }

    if (m_hContext)
    {
        m_hContext->Release();
        m_hContext = NULL;
    }
}

BOOL VideoDXGICaptor::AttatchToThread(VOID)
{
    if (g_bAttach)
    {
        return TRUE;
    }
    
    HDESK hCurrentDesktop = OpenInputDesktop(0, FALSE, GENERIC_ALL);
    if (!hCurrentDesktop)
    {
        return FALSE;
    }

    // Attach desktop to this thread
    BOOL bDesktopAttached = SetThreadDesktop(hCurrentDesktop);
    CloseDesktop(hCurrentDesktop);
    hCurrentDesktop = NULL;

    g_bAttach = TRUE;

    return bDesktopAttached;
}

BOOL VideoDXGICaptor::CaptureImage(RECT &rect, void *pData, INT &nLen)
{
    return QueryFrame(pData, nLen);
}
BOOL VideoDXGICaptor::CaptureImage(void *pData, INT &nLen)
{
    return QueryFrame(pData, nLen);
}
BOOL VideoDXGICaptor::ResetDevice()
{
    Deinit();
    return Init();
}
BOOL VideoDXGICaptor::QueryFrame(void *pImgData, INT &nImgSize)
{
    if (!m_bInit || !AttatchToThread())
    {
        return FALSE;
    }

    nImgSize = 0;

    IDXGIResource *hDesktopResource = NULL;
    DXGI_OUTDUPL_FRAME_INFO FrameInfo;
    HRESULT hr = m_hDeskDupl->AcquireNextFrame(0, &FrameInfo, &hDesktopResource);
    if (FAILED(hr))
    {
        //
        // 在一些win10的系统上,如果桌面没有变化的情况下，;
        // 这里会发生超时现象，但是这并不是发生了错误，而是系统优化了刷新动作导致的。;
        // 所以，这里没必要返回FALSE，返回不带任何数据的TRUE即可;
        //
        return TRUE;
    }

    //
    // query next frame staging buffer
    //
    ID3D11Texture2D *hAcquiredDesktopImage = NULL;
    hr = hDesktopResource->QueryInterface(__uuidof(ID3D11Texture2D), reinterpret_cast(&hAcquiredDesktopImage));
    RESET_OBJECT(hDesktopResource);
    if (FAILED(hr))
    {
        return FALSE;
    }

    //
    // copy old description
    //
    D3D11_TEXTURE2D_DESC frameDescriptor;
    hAcquiredDesktopImage->GetDesc(&frameDescriptor);

    //
    // create a new staging buffer for fill frame image
    //
    ID3D11Texture2D *hNewDesktopImage = NULL;
    frameDescriptor.Usage = D3D11_USAGE_STAGING;
    frameDescriptor.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
    frameDescriptor.BindFlags = 0;
    frameDescriptor.MiscFlags = 0;
    frameDescriptor.MipLevels = 1;
    frameDescriptor.ArraySize = 1;
    frameDescriptor.SampleDesc.Count = 1;
    hr = m_hDevice->CreateTexture2D(&frameDescriptor, NULL, &hNewDesktopImage);
    if (FAILED(hr))
    {
        RESET_OBJECT(hAcquiredDesktopImage);
        m_hDeskDupl->ReleaseFrame();
        return FALSE;
    }

    //
    // copy next staging buffer to new staging buffer
    //
    m_hContext->CopyResource(hNewDesktopImage, hAcquiredDesktopImage);

    RESET_OBJECT(hAcquiredDesktopImage);
    m_hDeskDupl->ReleaseFrame();

    //
    // create staging buffer for map bits
    //
    IDXGISurface *hStagingSurf = NULL;
    hr = hNewDesktopImage->QueryInterface(__uuidof(IDXGISurface), (void **)(&hStagingSurf));
    RESET_OBJECT(hNewDesktopImage);
    if (FAILED(hr))
    {
        return FALSE;
    }

    //
    // copy bits to user space
    //
    DXGI_MAPPED_RECT mappedRect;
    hr = hStagingSurf->Map(&mappedRect, DXGI_MAP_READ);
    if (SUCCEEDED(hr))
    {
        // nImgSize = GetWidth() * GetHeight() * 3;
        // PrepareBGR24From32(mappedRect.pBits, (BYTE*)pImgData, m_dxgiOutDesc.DesktopCoordinates);
        // mappedRect.pBits;
        // am_dxgiOutDesc.DesktopCoordinates;
        memcpy((BYTE*)pImgData, mappedRect.pBits, m_dxgiOutDesc.DesktopCoordinates.right * m_dxgiOutDesc.DesktopCoordinates.bottom * 4);
        hStagingSurf->Unmap();
    }

    RESET_OBJECT(hStagingSurf);
    return SUCCEEDED(hr);
}