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。

注意：本捕捉方法只能用于Windows 10；Windows 7 系统的DX查询不到相关接口，所以不能用的。

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：

//
//DXGICaptor.h
//#include <d3d11.h>
#include <dxgi1_2.h>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;
};//
//DXGICaptor.cpp
//#include "stdafx.h"
#include "DXGICaptor.h"
#include <windows.h>
#include <gdiplus.h>#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 supportedD3D_DRIVER_TYPE DriverTypes[] ={D3D_DRIVER_TYPE_HARDWARE,D3D_DRIVER_TYPE_WARP,D3D_DRIVER_TYPE_REFERENCE,};UINT NumDriverTypes = ARRAYSIZE(DriverTypes);// Feature levels supportedD3D_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<void**>(&hDxgiDevice));if (FAILED(hr)){return FALSE;}//// Get DXGI adapter//IDXGIAdapter *hDxgiAdapter = NULL;hr = hDxgiDevice->GetParent(__uuidof(IDXGIAdapter), reinterpret_cast<void**>(&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<void**>(&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 threadBOOL 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<void **>(&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);
}