求问一个多线程的例程C++(API)，情况如下所示：

Question

#include "stdafx.h"
#include "CameraDS.h"
#include "string"
#include <cv.h>
#include <highgui.h>

#include <stdio.h>
#include <iostream>

#include "windows.h"
#include <fstream>

using namespace std; 
int singlematching(IplImage *srcl, IplImage *srcr , IplImage *tp1);

int main() 
{
int cam_count;

//仅仅获取摄像头数目
cam_count = CCameraDS::CameraCount();
printf("There are %d cameras.\n", cam_count);

//获取所有摄像头的名称
for(int i=0; i < cam_count; i++)
{
char camera_name[1024]; 
int retval = CCameraDS::CameraName(i, camera_name, sizeof(camera_name) );

if(retval >0)
printf("Camera #%d's Name is '%s'.\n", i, camera_name);
else
printf("Can not get Camera #%d's name.\n", i);
}

if(cam_count==0)
return -1;

// 创建2个摄像头类
CCameraDS camera1;
CCameraDS camera2; 

if(! camera1.OpenCamera(0, false)) 
{
fprintf(stderr, "Can not open camera.\n");
return -1;
}
//打开第二个摄像头
camera2.OpenCamera(1, false); 

cvNamedWindow("cam1",1);
cvNamedWindow("cam2",1);
int nFrmNum = 0;

int k=0;

while(1)
{
//获取一帧
IplImage *pFrame1 = camera1.QueryFrame();
IplImage *pFrame2 = camera2.QueryFrame();
IplImage *fFrame1 = 0;
IplImage *fFrame2 = 0;
float scale=0.2;
CvSize dst_cvsize;

dst_cvsize.width=pFrame1->width*scale;
dst_cvsize.height=pFrame1->height*scale;
fFrame1=cvCreateImage(dst_cvsize,pFrame1->depth,pFrame1->nChannels);
fFrame2=cvCreateImage(dst_cvsize,pFrame1->depth,pFrame1->nChannels);
cvResize(pFrame1,fFrame1,CV_INTER_LINEAR);
cvResize(pFrame2,fFrame2,CV_INTER_LINEAR);
nFrmNum++;
DWORD dwStart = GetTickCount();
DWORD dwEnd = dwStart;
do
{
dwEnd = GetTickCount()-dwStart;
}while(dwEnd <1);

// 显示实时的摄像头视频
cvShowImage("cam1", fFrame1);
cvShowImage("cam2", fFrame2);
IplImage *tp1 = cvLoadImage("tr.bmp",1); 
int m;

if(k==5)
{
m=singlematching( pFrame2, pFrame1,tp1);\\运算
k=0;
}
k++;

//cvWaitKey(33);
int key = cvWaitKey(33);
if( key == 27 ) break;
}

camera1.CloseCamera(); //可不调用此函数，CCameraDS析构时会自动关闭摄像头
camera2.CloseCamera();
cvDestroyAllWindows();

return 0;
}

int singlematching(IplImage *srcl, IplImage *srcr ,IplImage *tp1)
{
}

Answer 1

#include <windows.h>typedef HANDLE HSEMAPHORE;#define P(hHandle) ::WaitForSingleObject(hHandle, INFINITE)#define V(hHandle) ::ReleaseSemaphore(hHandle, 1, NULL)#define Semaphore(lInitial, lMaximum) ::CreateSemaphore(NULL, lInitial, lMaximum, NULL)#define Thread(lpProc, lpParam) ::CreateThread(NULL, 0, lpProc, (LPVOID)lpParam, 0, NULL)#define Wait(nCount, lpHandles) ::WaitForMultipleObjects(nCount, lpHandles, TRUE, INFINITE)HSEMAPHORE n = Semaphore(0, 1);HSEMAPHORE s = Semaphore(1, 1);HSEMAPHORE e = Semaphore(100, 100);UINT count = 0;void Produce()void Consume()DWORD WINAPI Producer(LPVOID lpParameter){while (true){Produce();P(e);P(s);count++;printf("Producer: %d\n", count);V(s);V(n);}return 0;}DWORD WINAPI Consumer(LPVOID lpParameter){while (true){P(n);P(s);count--;printf("Consumer: %d\n", count);V(s);V(e);Consume();}return 0;}int main(){HANDLE hThreads[2];hThreads[0] = Thread(Producer, (LPVOID)NULL);hThreads[1] = Thread(Consumer, (LPVOID)NULL);Wait(2, hThreads);return 0;}

Answer 2

首先，你要有一个概念，多线程只是在有CPU空闲的程序中实现多个线程并行，从而使程序显得更”流畅“。多线程并不会让你的CPU运算能力得到提高。你的程序，或许可以用双线程：一个线程捕捉图像，一个线程处理数据。但要记住两点：1，两个线程间要加缓存2，当缓存已经满了的时候，捕捉线程应该要等处理数据的线程处理完缓存才继续捕捉。因此，并不能保证你用了双线程就会更加流畅，要你的的电脑运算能力。和捕捉图像的数据大小。