// MovieGrabberDLL.cpp : 定义 DLL 应用程序的入口点。

//



#include "stdafx.h"

#include "MovieGrabberDLL.h"

BOOL APIENTRY DllMain( HANDLE hModule, 

DWORD ul_reason_for_call, 

LPVOID lpReserved

)

...{

switch (ul_reason_for_call)

...{

case DLL_PROCESS_ATTACH: 

case DLL_THREAD_ATTACH:

case DLL_THREAD_DETACH:

case DLL_PROCESS_DETACH:

break;

}

return TRUE;

}



/**//**

* 抓取视频的截图

* @param aPath 视频文件的位置

* @return

*/

MOVIEGRABBERDLL_API HANDLE GrabMovieFrame(LPCTSTR aPath,int grayColorCountThreshold)

...{

HRESULT hr;

// 定义IMediaDet接口实例

CComPtr< IMediaDet > pDet;

hr = pDet.CoCreateInstance(__uuidof(MediaDet));

if (FAILED(hr))

return NULL;



// 将影片文件名转换成BSTR类型

CComBSTR openBSTR(aPath);

// 设置IMediaDet接口的文件关联

hr = pDet->put_Filename(openBSTR);

if (FAILED(hr))

return NULL;



// 从影片中检索视频流和音频流

long lStreams;

hr = pDet->get_OutputStreams(&lStreams);

if (FAILED(hr))

return NULL;



// 取出影片的视频流，因为帧的信息是保存在视频流中的

bool bFound = false;

for (int i=0; i
...{

GUID major_type;

hr = pDet->put_CurrentStream(i);

if (SUCCEEDED(hr))

hr = pDet->get_StreamType(&major_type);

if (FAILED(hr))

break;

if (major_type == MEDIATYPE_Video)

...{

bFound = true;

break;

}

}

if (!bFound)

return NULL;



long width = 0, height = 0; // 存储位图的宽和高（单位：象素）

AM_MEDIA_TYPE mt;

hr = pDet->get_StreamMediaType(&mt);

if (SUCCEEDED(hr))

...{

if ((mt.formattype == FORMAT_VideoInfo) && 

(mt.cbFormat >= sizeof(VIDEOINFOHEADER)))

...{

// 得到VIDEOINFOHEADER结构指针，VIDEOINFOHEADER结构包含一些与视频

// 有关的信息，其中含有BITMAPINFORHEADER结构

VIDEOINFOHEADER *pVih = (VIDEOINFOHEADER*)(mt.pbFormat);

width = pVih->bmiHeader.biWidth;

height = pVih->bmiHeader.biHeight;

if(height < 0 ) height *= -1;

}

else

hr = VFW_E_INVALIDMEDIATYPE;

MyFreeMediaType(mt); // 释放AM_MEDIA_TYPE结构

}

if (FAILED(hr))

return NULL;

return (HANDLE)LookforSuitableMovieFrame(pDet,width,height,grayColorCountThreshold);

}



/**//**

* 写入合适视频帧截图到磁盘

* @param pDet DirectShow的IMediaDet接口

* @param width 截图的长

* @param height 截图的宽

* @param grayColorCountThreshold 灰度颜色个数阈值

*/

HBITMAP LookforSuitableMovieFrame(IMediaDet* pDet,int width,int height,int grayColorCountThreshold)

...{

long size;

double time = 0.0;

double totaltime;



// 获取整个视频的时间长度

pDet->get_StreamLength(&totaltime);

// 每1秒,截取视频截图

for(time=0.0; time      ...{

// 获取bitmap的buffer大小

HRESULT hr = pDet->GetBitmapBits(time, &size, 0, width, height);

if (SUCCEEDED(hr)) 

...{

char *pBuffer = new char[size];

if (!pBuffer)

return NULL;

hr = pDet->GetBitmapBits(time, 0, pBuffer, width, height);

if (SUCCEEDED(hr))

...{

// Find the address of the start of the image data.

void *pData = pBuffer + sizeof(BITMAPINFOHEADER);

if(IsSuitableMovieFrame(pData,width,height,grayColorCountThreshold))

...{

BITMAPINFOHEADER *bmih = (BITMAPINFOHEADER*)pBuffer;

HDC hdcDest = GetDC(0);



BITMAPINFO bmi;

ZeroMemory(&bmi, sizeof(BITMAPINFO));

CopyMemory(&(bmi.bmiHeader), bmih, sizeof(BITMAPINFOHEADER));

HBITMAP hBitmap = CreateDIBitmap(hdcDest, bmih, CBM_INIT, 

pData, &bmi, DIB_RGB_COLORS);



delete[] pBuffer;

return hBitmap;

}

}

delete[] pBuffer;

}

}

return NULL;

}



/**//**

* 检测一个位图是否是合适的视频截图

* @param pData 位图的点色数组

* @param width 位图的长

* @param height 位图的宽

* @param grayColorCountThreshold 灰度颜色个数阈值

*/

bool IsSuitableMovieFrame(void* pData,int width,int height,int grayColorCountThreshold)

...{

BYTE* pixels = (BYTE*)pData;

int numGrayColor = 0;

int size = width*height;

int graycolor;

int i,j;

int* appearedcolors = new int[grayColorCountThreshold];

int numappearedcolors = 0;

for(i=0;i     ...{

// 计算当前点的灰度值，采用的RGB转换灰度的公式是GRAY = (R+G+B)/3

graycolor = (pixels[i*3] +pixels[i*3+1]+pixels[i*3+2])/3;

// 检测该灰度色是否之前出现过

for(j=0;j         ...{

if(graycolor == appearedcolors[j])

break;

}

if(j == numappearedcolors) // 如果是新的灰度颜色值

...{

numappearedcolors++;

if(numappearedcolors == grayColorCountThreshold) // 如果灰度颜色个数满足阈值

...{

delete[] appearedcolors;

return true; // 返回信息，合适

}

else

...{

appearedcolors[j] = graycolor; // 记录下该灰度颜色值

}

}

}

delete[] appearedcolors;

return false; // 返回信息，不合适

}



void MyFreeMediaType(AM_MEDIA_TYPE& mt)

...{

if(mt.cbFormat != 0)

...{

CoTaskMemFree((PVOID)mt.pbFormat);

mt.cbFormat = 0;

}



if (mt.pUnk != NULL)

...{

mt.pUnk->Release();

mt.pUnk = NULL;

}

}