How to get back image from contours?

Question

I am working on a project where I reduced my image to one object's contours(Actually its the pupil of the eye). Now I want to apply hough transform on the image that contains the contour of the pupil.But nothing happens. My guess is that you can apply hough transform on grayscale images only,

so I want to know how do I get back the greyscale portion of the contour of pupil I already detected so that I can apply hough transform on it.

Answer 1

assuming your video source is a normal webcam. i am not sure if hough can work. i tried and it did not work and may be if i spend more time it can work. but here's a way based on color that worked for me. result:https://s3-ap-southeast-1.amazonaws.com/kzl/eye.png

#include "stdafx.h"
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <iostream>
#include <time.h>
#include "opencv2/objdetect/objdetect.hpp"
using namespace cv;
using namespace std;


int s0=31,s1=96,s2=189, thresh=9;
String face_cascade_name = "lbpcascade_frontalface.xml";
String eyes_cascade_name = "haarcascade_eye_tree_eyeglasses.xml";
CascadeClassifier face_cascade,eyes_cascade;

void proc( Mat frame )
{
    double time = (double)getTickCount();
    std::vector<Rect> faces;
    Mat frame_gray;
    Mat eyeMask=Mat::zeros(frame.rows, frame.cols, CV_8UC1);;
    cvtColor( frame, frame_gray, CV_BGR2GRAY );
    equalizeHist( frame_gray, frame_gray );

    face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2,0, Size(50, 50));

    for( int i = 0; i < faces.size(); i++ )
    {
        Mat faceROI = frame_gray( faces[i] );
        std::vector<Rect> eyes;

        eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CV_HAAR_SCALE_IMAGE, Size(30, 30) );
        if( eyes.size() == 2)
        {
            Point center( faces[i].x + faces[i].width*0.5, faces[i].y + faces[i].height*0.5 );
            ellipse( frame, center, Size( faces[i].width*0.5, faces[i].height*0.5), 0, 0, 360, Scalar( 255, 0, 0 ), 2, 8, 0 );

            for( int j = 0; j < eyes.size(); j++ )
            {
                Rect roi =  Rect(faces[i].x+eyes[j].x,faces[i].y+eyes[j].y+(eyes[j].height*.25),eyes[j].width,eyes[j].height*.75);
                Mat eye(frame,roi);
                Mat eyeYuv;
                vector<Mat> eyechs;
                cvtColor(eye,eyeYuv,CV_BGR2YUV);
                split(eyeYuv,eyechs);
                Mat mask= eyechs[0];
                equalizeHist(mask,mask);
                threshold(mask,mask,thresh,255,CV_THRESH_BINARY_INV);
                mask.copyTo(eyeMask(roi));
            }
            imshow("mask",eyeMask);
        }

    }

    cvtColor( frame, frame, CV_BGR2YUV );
    for(int i=0;i<eyeMask.rows;i++)
    {
        for(int j=0;j<eyeMask.cols;j++)
        {
            if(eyeMask.at<uchar>(i,j)>0)
            {
                frame.at<Vec3b>(i,j)[0]=(frame.at<Vec3b>(i,j)[0]+s0)%255;
                frame.at<Vec3b>(i,j)[1]=(frame.at<Vec3b>(i,j)[1]+s1)%255;
                frame.at<Vec3b>(i,j)[2]=(frame.at<Vec3b>(i,j)[2]+s2)%255;
            }
        }
    }
    cvtColor( frame, frame, CV_YUV2BGR );

    time = ((double)getTickCount() - time)/getTickFrequency();
    std::ostringstream strs;
    strs << time;
    std::string text = strs.str();

    putText(frame, text, Point(30,30), FONT_HERSHEY_SCRIPT_SIMPLEX, .7, Scalar::all(255), 2,8);
    imshow( "cam", frame );
}

void run()
{
    namedWindow("cam", CV_WINDOW_KEEPRATIO);
    namedWindow("ctrl", CV_WINDOW_KEEPRATIO);
    namedWindow("mask", CV_WINDOW_KEEPRATIO);

    createTrackbar( "s0", "ctrl", &s0, 255, NULL );
    createTrackbar( "s1", "ctrl", &s1, 255, NULL );
    createTrackbar( "s2", "ctrl", &s2, 255, NULL );
    createTrackbar( "irisThresh", "ctrl", &thresh, 255, NULL );

    VideoCapture cap;
    cap.open(0);
    if( !cap.isOpened() )
    {
        cout << "cap error\n";
    }

    if( !face_cascade.load( face_cascade_name ) ){ cout << "face cascade error\n"; return ; };
    if( !eyes_cascade.load( eyes_cascade_name ) ){ cout << "eye cascade error\n"; return ; };
    Mat frame;
    cap >> frame;


    for(;;)
    {
        cap >> frame;
        resize(frame,frame,Size(320,240));
        proc(frame);
        char c = (char)waitKey(10);
        if( c == 27 )
            break;
    }
}

int main(int argc, char ** argv)
{
    run(); 
    cin.ignore(1);
    return 0;
}