继续是弱弱的做出了一份。
代码
#include "cv.h"
#include "highgui.h"
#include "stdio.h"
int main( int argc, char** argv ){
    IplImage *img1,*r,*g,*b;
    IplImage *clone1,*clone2;    
    cvNamedWindow("exercise3-7", CV_WINDOW_AUTOSIZE );    
    if (argv[1])
    {
        img1=cvLoadImage(argv[1]);
    }
    else return 1;
    
    
    CvSize Size1;
    Size1=cvGetSize(img1);
    r=cvCreateImage(Size1,IPL_DEPTH_8U,1);
    g=cvCreateImage(Size1,IPL_DEPTH_8U,1);
    b=cvCreateImage(Size1,IPL_DEPTH_8U,1);
    
    cvSplit(img1,b,g,r,NULL);
    //     BlueImage=cvCreateImage(Size1,IPL_DEPTH_8U,3);
    //    GreenImage=cvCreateImage(Size1,IPL_DEPTH_8U,3);
    //     RedImage=cvCreateImage(Size1,IPL_DEPTH_8U,3);
    //     cvMerge(0,0,b,0,BlueImage);
    //     cvMerge(0,g,0,0,GreenImage);
    //    cvMerge(0,0,r,0,RedImage);
    cvShowImage("exercise3-7", img1 );
    cvNamedWindow("g", CV_WINDOW_AUTOSIZE );
    IplImage *    GreenImage=cvCreateImage(Size1,IPL_DEPTH_8U,3);
    cvMerge(0,g,0,0,GreenImage);
    clone1=clone2=cvCloneImage(g);        
    double maximum,minimum;
    cvMinMaxLoc(g,&minimum,&maximum);
    unsigned char thresh = (unsigned char)((maximum - minimum)/2.0);
    cvmSetZero(clone1);
    cvAddS(clone1,cvScalar(thresh),clone1);
    
    
    
    
    //cvSetReal2D(clone1,0,0,10);
    cvmSetZero(clone2);
    
    cvCmp(g, clone1, clone2, CV_CMP_GE);
    
    cvSubS(g,cvScalar(thresh/2), g, clone2);
    
    cvShowImage("g", g);
    cvWaitKey(0);
    cvReleaseImage(&img1);    cvReleaseImage(&g);
    
    cvDestroyWindow("exercise3-7");
    
    return 0;
}