Thresholding of a binary image using trackbar

trackbar_mono.cpp

#include "opencv2/opencv.hpp"

#define PIX(img,i,j,k) (((uchar*)img->imageData)[i*img->widthStep+j*img->nChannels+k])

IplImage* createbinary(IplImage *img, int thresh)
{
        int i,j,ht,wd;
        ht=img->height;
        wd=img->width;
        
        IplImage* grey=cvCreateImage(cvSize(wd,ht),IPL_DEPTH_8U,1);
        for(i=0;i<ht;i++)
                for(j=0;j<wd;j++)
                {
                        PIX(grey,i,j,0)=(.33*PIX(img,i,j,0)+.33*PIX(img,i,j,1)+.33*PIX(img,i,j,2));
                        if(PIX(grey,i,j,0)>thresh)
                                PIX(grey,i,j,0)=255;
                        else PIX(grey,i,j,0)=0;
                }
        return grey;
}

int main()
{
        int thresh = 127;
        CvCapture* capture=cvCreateCameraCapture(0);
        IplImage *frame,*grey;
        char win[]="video_stream";
        char win2[]="trackbar";

        cvNamedWindow(win,CV_WINDOW_AUTOSIZE);
        cvNamedWindow(win2,CV_WINDOW_AUTOSIZE);
        cvCreateTrackbar("trackbarwin",win2,&thresh,255);

        while(1)
        {
                frame = cvQueryFrame(capture);
                grey = createbinary(frame, thresh);
                cvShowImage(win,frame);
                cvShowImage(win2,grey);
                char c = cvWaitKey(33);
                if(c==27)break;
        }
        
        cvReleaseCapture(&capture);
        cvReleaseImage(&frame);
        cvReleaseImage(&grey);
        cvDestroyWindow(win);
        cvDestroyWindow(win2);
        return 0;
}