检测正方形后运行命令的c++算法

Question

我有用于检测正方形的 opencv 代码。现在我想在检测正方形后，代码运行另一个命令。

代码如下:

#include "cv.h"
#include "cxcore.h"
#include "highgui.h"
#include "math.h"
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <sstream>

using namespace std;

double angle( CvPoint* pt1, CvPoint* pt2, CvPoint* pt0 )
{
    double dx1 = pt1->x - pt0->x;
    double dy1 = pt1->y - pt0->y;
    double dx2 = pt2->x - pt0->x;
    double dy2 = pt2->y - pt0->y;
    return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);
} // angle

IplImage* findSquares4(  IplImage* img,  CvMemStorage* storage )
{
    double s = 0,  t = 0;
    int sdetect =0, sqdetect = 0,sqt = 0;
    CvSeq* contours;
    CvSeq* result;
    CvSeq* squares  =  cvCreateSeq(  0,  sizeof( CvSeq),  sizeof( CvPoint),  storage );

    IplImage* cny = cvCreateImage(cvGetSize(img), 8, 1);

    cvCanny(img, cny, 5, 100, 3);

    cvNamedWindow("canny",CV_WINDOW_AUTOSIZE);
    cvShowImage("canny",cny);

    cvFindContours(  cny,  storage,  &contours,  sizeof( CvContour),  CV_RETR_LIST,  CV_CHAIN_APPROX_SIMPLE,  cvPoint( 0, 0) );

    while(  contours )
    {
        result  =  cvApproxPoly(    contours,
                                sizeof( CvContour),
                                storage,
                                CV_POLY_APPROX_DP,
                                cvContourPerimeter( contours)*0.02,  0 );

        if(  result->total  == 4 &&
             fabs( cvContourArea( result, CV_WHOLE_SEQ)) > 1000 &&
             cvCheckContourConvexity( result) )
        {
            s  =  0;
            for(  int i = 2; i < 5; i++ )
            {
                {
                    t  =  fabs( angle(
                                ( CvPoint*)cvGetSeqElem(  result,  i ),
                                ( CvPoint*)cvGetSeqElem(  result,  i-2 ),
                                ( CvPoint*)cvGetSeqElem(  result,  i-1 )));
                    s  =  s > t ? s : t;
                    cout << "s = " << s<< endl;
                    cout << "t = " << t<< endl;
                }
            } // for
            if(  s < 0.3 )
                for(  int i  =  0; i < 4; i++ )
                    cvSeqPush(  squares,
                          ( CvPoint*)cvGetSeqElem(  result,  i ));
        } // if

    contours  =  contours->h_next;

    } // while
    if ((squares->total/4) = 1)
    {
        sdetect = 1;
    } / /if
    else
    {
        sdetect = 2;
        sleep(0.5);
    } // else

    if (sqdetect != sdetect)
    {
        sqdetect=sdetect;
        switch(sqdetect)
        {
            case 0 : system(NULL) ; break;
            case 2 : cout<< "no "<< endl; break;
            case 1 : system("./ambil1.sh"); break;
        } // switch
    } // if
    sdetect = 0;

    cout<<"Persegi : "<< squares->total/4 <<endl;

    cvReleaseMemStorage(&storage);
    cvClearSeq(squares);

} // findSquares4

void drawSquares(IplImage *img, CvSeq* squares )
{
    CvFont font;
    cvInitFont( &font, CV_FONT_HERSHEY_SIMPLEX, 0.4f, 0.4f, 0,1, 8 );
    int i,j,sdetect,sqdetect = 0;
    CvSeqReader reader;
    cvStartReadSeq( squares, &reader, 0 );

    for( i = 0; i < squares->total; i += 4 )
    {
        j++;
        CvPoint pt[4], *rect = pt;
        int count = 4;

         // read 4 vertices
        memcpy( pt, reader.ptr, squares->elem_size );
        CV_NEXT_SEQ_ELEM( squares->elem_size, reader );
        memcpy( pt + 1, reader.ptr, squares->elem_size );
        CV_NEXT_SEQ_ELEM( squares->elem_size, reader );
        memcpy( pt + 2, reader.ptr, squares->elem_size );
        CV_NEXT_SEQ_ELEM( squares->elem_size, reader );
        memcpy( pt + 3, reader.ptr, squares->elem_size );
        CV_NEXT_SEQ_ELEM( squares->elem_size, reader );

        cvPutText( img, "SQUARE", pt[i], &font, CV_RGB(20,255,0));

        cvPolyLine( img, &rect, &count, 1, 1, CV_RGB(200,0,0), 4, CV_AA, 0 );
    } // for

cvClearSeq(squares);
}  // drawSquares

但我得到的是程序变得滞后。那么为执行 system (./ambil1.sh) 设置条件的正确算法是什么？

Answer 1

程序一直等到从属命令完成。在此期间它不会响应。

如果这就是您的需要，system 就足够了。

如果你想即发即弃，你可以使用 fork/exec 对，或者只使用 shell & 运算符在后台运行东西。

如果您需要启动、更改程序的行为，然后在从属命令完成时将其改回，您几乎必须使用 fork/exec/SIGCHLD/waitpid 组合。