DXGI截取桌面图像

DXGI截取桌面图像

使用DXGI截取桌面图像效率高,cpu占用低,是抓取桌面图像的好方法(只支持win8及以上)。

使用DXGI截取桌面图像主要分为下面三个步骤。

  1. 创建ID3D11DeviceID3D11DeviceContext对象。

  2. 获取IDXGIOutputDuplication对象。

  3. 调用AcquireNextFrame函数获取桌面纹理。

头文件与库

请在源代码文件添加如下头文件与库。

#include 
#include 

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

定义桌面捕获类

// DXGIDuplicator.h

#include 
#include 
#include 

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

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

    bool InitD3D11Device();

    bool InitDuplication();

    bool GetDesktopFrame(ID3D11Texture2D** texture);
    
    // 友元函数,在main函数里面会用到,需要访问其私有成员
    friend void SaveDesktopImage(std::string filename, ID3D11Texture2D* texture, DXGIDuplicator* duplicator);

private:
    ID3D11Device* device_ = nullptr;
    ID3D11DeviceContext* deviceContext_ = nullptr;
    IDXGIOutputDuplication* duplication_ = nullptr;
};

类中定义的方法对应获取桌面图像的三个步骤,最终的图像数据保存在texture中,注意这是一个二级指针。AcquireNextFrame方法来自于duplication_对象,所以调用一系列的函数是为了得到duplication_对象。

桌面捕获类实现

// DXGIDuplicator.cpp

#include "DXGIDuplicator.h"

// 构造函数,里面什么也不做
DXGIDuplicator::DXGIDuplicator()
{
}

// 析构函数,释放相关对象
DXGIDuplicator::~DXGIDuplicator()
{
    if (duplication_)
    {
        duplication_->Release();
    }
    if (device_)
    {
        device_->Release();
    }
    if (deviceContext_)
    {
        deviceContext_->Release();
    }
}

InitD3D11Device

实现函数InitD3D11Device。一般是固定步骤,只需要记住D3D11CreateDevice这个函数即可,当然也有别的方法获取ID3D11Device和ID3D11DeviceContext,感兴趣的可以搜搜。

bool DXGIDuplicator::InitD3D11Device()
{
    D3D_DRIVER_TYPE DriverTypes[] =
    {
        D3D_DRIVER_TYPE_HARDWARE,
        D3D_DRIVER_TYPE_WARP,
        D3D_DRIVER_TYPE_REFERENCE,
    };
    UINT NumDriverTypes = ARRAYSIZE(DriverTypes);

    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;

    for (UINT DriverTypeIndex = 0; DriverTypeIndex < NumDriverTypes; ++DriverTypeIndex)
    {
        HRESULT hr = D3D11CreateDevice(
            nullptr,
            DriverTypes[DriverTypeIndex],
            nullptr, 0,
            FeatureLevels,
            NumFeatureLevels,
            D3D11_SDK_VERSION,
            &device_,
            &FeatureLevel,
            &deviceContext_);
        if (SUCCEEDED(hr))
        {
            break;
        }
    }

    if (device_ == nullptr || deviceContext_ == nullptr)
    {
        return false;
    }

    return true;
}

InitDuplication

实现函数InitDuplication。这里又分为好几个步骤,如下:

  1. 获取IDXGIDevice对象

  2. 获取IDXGIAdapter对象

  3. 获取IDXGIOutput对象

  4. 获取IDXGIOutput1对象

  5. 获得IDXGIOutputDuplication对象

从下图中可知一个adapter可对应多个output,所以代码中使用EnumOutputs来枚举可用的输出。其实adapter也有可能有多个,这里暂不考虑。

图中的IDXGIOutput1、IDXGIOutput2等与代码中的IDXGIOutput1对象并无关系。图中数字只表示输出口的个数,而代码中代表了版本。

bool DXGIDuplicator::InitDuplication()
{
    HRESULT hr = S_OK;

    IDXGIDevice* dxgiDevice = nullptr;
    hr = device_->QueryInterface(__uuidof(IDXGIDevice), reinterpret_cast(&dxgiDevice));
    if (FAILED(hr))
    {
        return false;
    }
    
    IDXGIAdapter* dxgiAdapter = nullptr;
    hr = dxgiDevice->GetAdapter(&dxgiAdapter);
    dxgiDevice->Release();
    if (FAILED(hr))
    {
        return false;
    }

    UINT output = 0;
    IDXGIOutput* dxgiOutput = nullptr;
    while (true)
    {
        hr = dxgiAdapter->EnumOutputs(output++, &dxgiOutput);
        if (hr == DXGI_ERROR_NOT_FOUND)
        {
            return false;
        }
        else
        {
            DXGI_OUTPUT_DESC desc;
            dxgiOutput->GetDesc(&desc);
            int width = desc.DesktopCoordinates.right - desc.DesktopCoordinates.left;
            int height = desc.DesktopCoordinates.bottom - desc.DesktopCoordinates.top;
            break;
        }
    }
    dxgiAdapter->Release();

    IDXGIOutput1* dxgiOutput1 = nullptr;
    hr = dxgiOutput->QueryInterface(__uuidof(IDXGIOutput1), reinterpret_cast(&dxgiOutput1));
    dxgiOutput->Release();
    if (FAILED(hr))
    {
        return false;
    }

    hr = dxgiOutput1->DuplicateOutput(device_, &duplication_);
    dxgiOutput1->Release();
    if (FAILED(hr))
    {
        return false;
    }

    return true;
}

获取桌面图像

获取桌面图像后还不能直接使用,因为图像还在显存中,需要拷贝到内存里面才可以直接读写。

bool DXGIDuplicator::GetDesktopFrame(ID3D11Texture2D** texture)
{
    HRESULT hr = S_OK;
    DXGI_OUTDUPL_FRAME_INFO frameInfo;
    IDXGIResource* resource = nullptr;
    ID3D11Texture2D* acquireFrame = nullptr;

    hr = duplication_->AcquireNextFrame(0, &frameInfo, &resource);
    if (FAILED(hr))
    {
        if (hr == DXGI_ERROR_WAIT_TIMEOUT)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    hr = resource->QueryInterface(__uuidof(ID3D11Texture2D), reinterpret_cast(&acquireFrame));
    resource->Release();
    if (FAILED(hr))
    {
        return false;
    }

    D3D11_TEXTURE2D_DESC desc;
    acquireFrame->GetDesc(&desc);
    desc.Usage = D3D11_USAGE_STAGING;
    desc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
    desc.BindFlags = 0;
    desc.MiscFlags = 0;
    desc.MipLevels = 1;
    desc.ArraySize = 1;
    desc.SampleDesc.Count = 1;
    device_->CreateTexture2D(&desc, NULL, texture);
    if (texture && *texture)
    {
        deviceContext_->CopyResource(*texture, acquireFrame);
    }
    acquireFrame->Release();

    hr = duplication_->ReleaseFrame();
    if (FAILED(hr))
    {
        return false;
    }

    return true;
}

主函数实现

// main.cpp

#include 
#include 

#include "DXGIDuplicator.h"

void SaveBmp(std::string filename, const uint8_t* data, int width, int height)
{
    HANDLE hFile = CreateFileA(filename.c_str(), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == NULL)
    {
        return;
    }
    // 已写入字节数
    DWORD bytesWritten = 0;
    // 位图大小,颜色默认为32位即rgba
    int bmpSize = width * height * 4;

    // 文件头
    BITMAPFILEHEADER bmpHeader;
    // 文件总大小 = 文件头 + 位图信息头 + 位图数据
    bmpHeader.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + bmpSize;
    // 固定
    bmpHeader.bfType = 0x4D42;
    // 数据偏移,即位图数据所在位置
    bmpHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    // 保留为0
    bmpHeader.bfReserved1 = 0;
    // 保留为0
    bmpHeader.bfReserved2 = 0;
    // 写文件头
    WriteFile(hFile, (LPSTR)&bmpHeader, sizeof(bmpHeader), &bytesWritten, NULL);

    // 位图信息头
    BITMAPINFOHEADER bmiHeader;
    // 位图信息头大小
    bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    // 位图像素宽度
    bmiHeader.biWidth = width;
    // 位图像素高度,负高度即上下翻转
    bmiHeader.biHeight = -height;
    // 必须为1
    bmiHeader.biPlanes = 1;
    // 像素所占位数
    bmiHeader.biBitCount = 32;
    // 0表示不压缩
    bmiHeader.biCompression = 0;
    // 位图数据大小
    bmiHeader.biSizeImage = bmpSize;
    // 水平分辨率(像素/米)
    bmiHeader.biXPelsPerMeter = 0;
    // 垂直分辨率(像素/米)
    bmiHeader.biYPelsPerMeter = 0;
    // 使用的颜色,0为使用全部颜色
    bmiHeader.biClrUsed = 0;
    // 重要的颜色数,0为所有颜色都重要
    bmiHeader.biClrImportant = 0;

    // 写位图信息头
    WriteFile(hFile, (LPSTR)&bmiHeader, sizeof(bmiHeader), &bytesWritten, NULL);
    // 写位图数据
    WriteFile(hFile, data, bmpSize, &bytesWritten, NULL);
    CloseHandle(hFile);
}

void SaveDesktopImage(std::string filename, ID3D11Texture2D* texture2D, DXGIDuplicator* duplicator)
{
    D3D11_TEXTURE2D_DESC desc;
    texture2D->GetDesc(&desc);
    D3D11_MAPPED_SUBRESOURCE mappedResource;
    duplicator->deviceContext_->Map(texture2D, 0, D3D11_MAP_READ, 0, &mappedResource);
    
    size_t imageSize = desc.Width * desc.Height * 4;
    uint8_t* rgba = (uint8_t*)malloc(imageSize);
    if (rgba == nullptr)
    {
        return;
    }
    memset(rgba, 0, imageSize);
    uint8_t* pData = (uint8_t*)mappedResource.pData;
    for (size_t i = 0; i < desc.Height; i++)
    {
        memcpy(rgba + i * desc.Width * 4, pData + i * mappedResource.RowPitch, desc.Width * 4);
    }
    SaveBmp(filename, rgba, desc.Width, desc.Height);
    free(rgba);
}

int main()
{
    DXGIDuplicator* duplicator = new DXGIDuplicator;

    if (!duplicator->InitD3D11Device())
    {
        std::cout << "Init d3d11 device failed" << std::endl;
        return 1;
    }

    if (!duplicator->InitDuplication())
    {
        std::cout << "Init duplication failed" << std::endl;
        return 1;
    }

    ID3D11Texture2D* texture2D = nullptr;
    int num = 0;
    while (num < 10)
    {
        if (!duplicator->GetDesktopFrame(&texture2D))
        {
            std::cout << "Acquire frame failed" << std::endl;
            return 1;
        }
        if (texture2D == nullptr)
        {
            std::cout << "Acquire frame timeout" << std::endl;
            continue;
        }
        std::string filename = "desktop" + std::to_string(num) + ".bmp";
        SaveDesktopImage(filename, texture2D, duplicator);
        std::cout << filename << std::endl;
        texture2D->Release();
        texture2D = nullptr;
        num++;
        Sleep(500);
    }

    delete duplicator;
    return 0;
}

代码中对异常处理较为简单,没有细分异常情况。

参考文献

http://cn.voidcc.com/question/p-chbugccl-ug.html
https://docs.microsoft.com/zh-cn/windows/win32/direct3ddxgi/desktop-dup-api
http://t.zoukankan.com/wickedpriest-p-13568190.html

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