OpenCV使用VideoInput库从摄像头捕获视频

转自http://kqwd.blog.163.com/blog/static/412234482010611105013322/

OpenCV具有强大的图像处理功能，处理视频也是毫不逊色。只是其自带的HighGUI并非是具有工业强度的模块，不适合最终提供给客户，仅仅是方便程序开发阶段的调试。其中跟视频捕获相关的cvCreateCameraCapture或cvCaptureFromCAM函数可以方便的从摄像头捕获视频，但这两个函数在Windows中都是由较为低效的VFW机制实现的，不适合在最终产品中使用。

在Windows中使用DirectShow可以高效的从摄像头捕获视频，但使用较为复杂。OpenCV中文网的YuShiQi提供了一个基于DirectShow实现的摄像头捕获类，但试用后效果一般，速度并没有明显的提高。

新版的OpenCV（OpenCV
2.0及以后版本）提供了第三方的VideoInput库，该库实现了基于DirectShow的视频捕获，使用方便、功能强大，速度也很快。另外还有一个意外发现——腾讯QQ的视频捕获貌似用的也是这个库哦~~

好了，下面就说说如何使用这个库

如果你的OpenCV版本低于2.0，请先去http://muonics.net/school/spring05/videoInput/

下载VideoInput，我这里需要翻墙才能上去。如果使用2.0及以后版本则自带该库。

首先需要在代码中包含VideoInput的头文件

#include <videoInput.h>

         这个文件的默认路径是C:OpenCV2.13rdpartyinclude

         静态链接库的默认路径是C:OpenCV2.13rdpartylib

         请先设置IDE中头文件和库文件的搜索路径。

 

下面给出一个读取并显示摄像头画面的实例

int width=320;

int height=240;

IplImage *pRgb=cvCreateImage(cvSize(width,height), IPL_DEPTH_8U, 3);

videoInput video;//创建视频捕获对象

video.setupDevice(0, width, height);//配置设备

video.showSettingsWindow(0);//该语句可以显示视频设置窗口，可以去掉

while(1)

{

   if(video.isFrameNew(0))

   {

        video.getPixels(0,
(unsigned char *)pRgb->imageData, false, true);//获取一帧

        //cvFlip(pRgb,NULL,1);//加上这句就水平翻转画面

        char c=cvWaitKey(1);

        if(c==27) break;//按ESC退出

        cvShowImage(“Video”,
pRgb);

   }

}

 

有朋友提出编译时可能会遇到如下错误：

"fatal error LNK1104: cannot open file 'atlthunk.lib'"

如果遇到此错误，请在文件的开头加入如下语句：

#pragma comment(linker, "/NODEFAULTLIB:atlthunk.lib")

这个类库还提供了非常强大的功能，具体函数可以查看videoInput.h头文件。下面附上videoInput类的共有成员函数列表和相关说明。

//turns off console messages - default is to print messages

static void setVerbose(bool _verbose);

 

//Functions in rough order they should be used.

static int listDevices(bool silent
= false);

 

//needs to be called after listDevices - otherwise returns NULL

static char *
getDeviceName(int deviceID);

 

//choose to use callback based capture - or single threaded

void setUseCallback(bool useCallback);

 

//call before setupDevice

//directshow will try and get the closest possible framerate to what is requested

void setIdealFramerate(int deviceID, int idealFramerate);

 

//some devices will stop delivering frames after a while - this method gives you the option to try and reconnect

//to a device if videoInput detects that a device has stopped delivering frames.

//you MUST CALL isFrameNew every app loop for this to have any effect

void setAutoReconnectOnFreeze(int deviceNumber, bool doReconnect, int numMissedFramesBeforeReconnect);

 

//Choose one of these four to setup your device

bool setupDevice(int deviceID);

bool setupDevice(int deviceID, int w, int h);

 

//These two are only for capture cards

//USB and Firewire cameras souldn't specify connection

bool setupDevice(int deviceID, int connection);

bool setupDevice(int deviceID, int w, int h, int connection);

 

//If you need to you can set your NTSC/PAL/SECAM

//preference here. if it is available it will be used.

//see #defines above for available formats - eg VI_NTSC_M or VI_PAL_B

//should be called after setupDevice

//can be called multiple times

bool setFormat(int deviceNumber, int format);

 

//Tells you when a new frame has arrived - you should call this if you have specified setAutoReconnectOnFreezeto true

bool isFrameNew(int deviceID);

 

bool isDeviceSetup(int deviceID);

   

//Returns the pixels - flipRedAndBlue toggles RGB/BGR flipping - and you can flip the image too

unsigned char *
getPixels(int deviceID, bool flipRedAndBlue
= true, bool flipImage
= false);

 

//Or pass in a buffer for getPixels to fill returns true if successful.

bool getPixels(int id, unsigned char *
pixels, bool flipRedAndBlue = true, bool flipImage
= false);

 

//Launches a pop up settings window

//For some reason in GLUT you have to call it twice each time.

void showSettingsWindow(int deviceID);

 

//Manual control over settings thanks.....

//These are experimental for now.

bool setVideoSettingFilter(int deviceID, long Property, long lValue, long Flags
= NULL, bool useDefaultValue =false);

bool setVideoSettingFilterPct(int deviceID, long Property, float pctValue, long Flags
= NULL);

bool getVideoSettingFilter(int deviceID, long Property, long &min, long &max, long &SteppingDelta, long¤tValue, long &flags, long &defaultValue);

 

bool setVideoSettingCamera(int deviceID, long Property, long lValue, long Flags
= NULL, bool useDefaultValue =false);

bool setVideoSettingCameraPct(int deviceID, long Property, float pctValue, long Flags
= NULL);

bool getVideoSettingCamera(int deviceID, long Property, long &min, long &max, long &SteppingDelta, long¤tValue, long &flags, long &defaultValue);

 

//bool setVideoSettingCam(int deviceID, long Property, long lValue, long Flags = NULL, bool useDefaultValue = false);

 

//get width, height and number of pixels

int  getWidth(int deviceID);

int  getHeight(int deviceID);

int  getSize(int deviceID);

 

//completely stops and frees a device

void stopDevice(int deviceID);

 

//as above but then sets it up with same settings

bool restartDevice(int deviceID);

 

//number of devices available

int  devicesFound;