DirectShow实现视频的实时显示并抓图，可以设置视频参数

DirectShow抓图其实是使用IBasicVideo（IID_IBasicVideo）接口获取数据源，进行存储即可。

IGraphBuilder* m_pGraphBuild = NULL;
hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC,IID_IGraphBuilder, (void**)&m_pGraphBuild);

完整代码如下：

void CCamera::CapturePicture(char* pFileName)
{
    IBasicVideo* pBasicVideo = NULL;
    m_pGraphBuild->QueryInterface(IID_IBasicVideo, (void**)&pBasicVideo);


    long bitmapSize;
    char* buffer;
    HRESULT hr = pBasicVideo->GetCurrentImage(&bitmapSize, 0);
    if (SUCCEEDED(hr))
    {
        buffer = new char[bitmapSize];
        hr = pBasicVideo->GetCurrentImage(&bitmapSize, (long*)buffer);


        BITMAPFILEHEADER hdr;  //定义位图变量
        LPBITMAPINFOHEADER lpbi; //是个指针,指向BMP头的
        lpbi = (LPBITMAPINFOHEADER)buffer;

        int nColor = 0;
        if (lpbi->biBitCount <= 8)
        {
            nColor = 1 << lpbi->biBitCount;
        }

        // Fill in the fields of the file header 
        hdr.bfType = ((WORD)('M' << 8) | 'B');// 位图类别is always "BM"
        hdr.bfSize = bitmapSize + sizeof(hdr);  //BMP图像文件的大小
        hdr.bfReserved1 = 0;  //总为0
        hdr.bfReserved2 = 0;   //总为0
        hdr.bfOffBits = (DWORD)(sizeof(BITMAPFILEHEADER) +  //BMP图像数据的地址
            lpbi->biSize + nColor * sizeof(RGBQUAD));


        FILE* fp = fopen("1.bmp", "wb");
        fwrite(&hdr, sizeof(BITMAPFILEHEADER),1,fp);
        fwrite(buffer, bitmapSize, 1, fp);
        fclose(fp);

    }
}