Adaptive thresholding for binary video from live camera feed

adaptivethresholding.cpp

#include "opencv2/opencv.hpp"

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

int findmedian(IplImage* img)
{
        int intensities[256];
        int i,j,temp=0;
        for(i=0;i<256;i++)
                intensities[i]=0;

        for(i=0;i<img->height;i++)
                for(j=0;j<img->width;j++)
                        intensities[PIX(img,i,j,0)]++;

        for(i=0;i<256;i++){
                temp += intensities[i];
                if(temp > (img->width*img->height)/2)
                        break;
        }
        return i;
}

IplImage* createbinary(IplImage *img)
{
        int i,j,ht,wd,thresh;
        ht=img->height;
        wd=img->width;

        IplImage* output = cvCreateImage(cvSize(wd,ht),IPL_DEPTH_8U,1);
        for(i=0;i<ht;i++)
                for(j=0;j<wd;j++)
                        PIX(output,i,j,0)=(.33*PIX(img,i,j,0)+.56*PIX(img,i,j,1)+.11*PIX(img,i,j,2));

        // now output is a greyscale image

        thresh = findmedian(output);
        for(i=0;i<ht;i++)
                for(j=0;j<wd;j++)
                        PIX(output,i,j,0)=(PIX(output,i,j,0)>thresh)?255:0;
        //  output now has been converted to a binary image
        return output;
}



int main()
{
        CvCapture* capture=cvCreateCameraCapture(0);
        IplImage *frame,*output;
        char win[]="video_stream";
        char win2[]="outputscale";

        cvNamedWindow(win,CV_WINDOW_AUTOSIZE);
        cvNamedWindow(win2,CV_WINDOW_AUTOSIZE);

        while(1)
        {
                frame = cvQueryFrame(capture);
                output = createbinary(frame);
                cvShowImage(win,frame);
                cvShowImage(win2,output);
                char c=cvWaitKey(33);
                if(c==27)
                        break;
        }

        cvReleaseCapture(&capture);
        cvReleaseImage(&frame);
        cvReleaseImage(&output);
        cvDestroyWindow(win);
        cvDestroyWindow(win2);
        return 0;
}