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Canny_P_images.cpp
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Canny_P_images.cpp
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/************************************************
Canny edge detection with parallelisation
************************************************/
#include <iostream>
#include <bits/stdc++.h>
#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/opencv.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <opencv2/objdetect/objdetect.hpp>
#include <math.h>
#include <omp.h>
using namespace cv;
using namespace std;
int main()
{
string filename;
cout<<"Enter filename:";
cin>> filename;
// Reading image
Mat img = imread(filename);
// Displaying image
//imshow("Original Image",img);
//waitKey(0);
// Converting to grayscale
Mat img_gray,image_gray;
cvtColor(img,image_gray,CV_RGB2GRAY);
GaussianBlur( image_gray, img_gray, Size(5,5), 3, 3);
// Displaying grayscale image
//imshow("Original Image",img_gray);
//waitKey(0);
cv::Mat Gx, Gy; int ksize=3;
Mat abs_grad_x, abs_grad_y;
cv::Sobel(img_gray, Gx, CV_64F, 1, 0, ksize);
convertScaleAbs( Gx, abs_grad_x );
cv::Sobel(img_gray, Gy, CV_64F, 0, 1, ksize);
convertScaleAbs( Gy, abs_grad_y );
Mat grad;
addWeighted( abs_grad_x, 0.5, abs_grad_y, 0.5, 0, grad );
//imshow("Sobel Image",grad);
//waitKey(0);
//Canny edge detection
// Performing Non-Maximum Surpression
float theta; // Calculate intensity gradient vector theta=atan2(Gy,Gx);
Mat nonMaxSupp= Mat(grad.rows-2, grad.cols-2, CV_8UC1); //CV_8UC1 is 8-bit single channel image i.e grayscale
int i,j;
#pragma omp parallel for default(shared) private(i,j,theta) num_threads(3) ordered schedule(dynamic,120) collapse(2)
for(i=1; i<Gx.rows-1; i++)
{
for(j=1; j<Gx.cols-1; j++)
{
//if(gradient_x.at<uchar>(i,j) ==0) //Arctan Fix
// theta = 90;
//else
theta = atan2(Gy.at<uchar>(i,j),Gx.at<uchar>(i,j))*(180/3.14);
//theta = atan(gradient_y.at<uchar>(i,j)/gradient_x.at<uchar>(i,j))*(180/3.14);
//cout<<theta<<endl;
//if(theta>max)
// max=theta;
nonMaxSupp.at<uchar>(i-1, j-1) = grad.at<uchar>(i,j);
// For horizontal edge
if(((-22.5 < theta) && (theta <= 22.5)) || ((157.5 < theta) && (theta <= -157.5)))
{
if ((grad.at<uchar>(i,j) < grad.at<uchar>(i,j+1)) || (grad.at<uchar>(i,j) < grad.at<uchar>(i,j-1)))
nonMaxSupp.at<uchar>(i-1, j-1) = 0;
}
//For vertical edge
if (((-112.5 < theta) && (theta <= -67.5)) || ((67.5 < theta) && (theta <= 112.5)))
{
if ((grad.at<uchar>(i,j) < grad.at<uchar>(i+1,j)) || (grad.at<uchar>(i,j) < grad.at<uchar>(i-1,j)))
nonMaxSupp.at<uchar>(i-1, j-1) = 0;
}
// For 135 degree or -45 degree edge
if (((-67.5 < theta) && (theta <= -22.5)) || ((112.5 < theta) && (theta <= 157.5)))
{
if ((grad.at<uchar>(i,j) < grad.at<uchar>(i-1,j+1)) || (grad.at<uchar>(i,j) < grad.at<uchar>(i+1,j-1)))
nonMaxSupp.at<uchar>(i-1, j-1) = 0;
}
// For 45 Degree Edge
if (((-157.5 < theta) && (theta <= -112.5)) || ((22.5 < theta) && (theta <= 67.5)))
{
if ((grad.at<uchar>(i,j) < grad.at<uchar>(i+1,j+1)) || (grad.at<uchar>(i,j) < grad.at<uchar>(i-1,j-1)))
nonMaxSupp.at<uchar>(i-1, j-1) = 0;
}
/*else
{
nonMaxSupp.at<uchar>(i-1, j-1) = 255;
}
*/
}
}
//cout<<endl<<"max"<<max;
imshow("Non-Maximum Surpression",nonMaxSupp);
waitKey(0);
// Hysterisis Thresholding
int low=20,high=40;
if(low > 255)
low = 255;
if(high > 255)
high = 255;
Mat EdgeMat = Mat(nonMaxSupp.rows, nonMaxSupp.cols, nonMaxSupp.type());
double start,end,diff;
start = omp_get_wtime();
#pragma omp parallel for default(shared) private(i,j) num_threads(4) ordered schedule(dynamic,120) collapse(2)
for (i=0; i<nonMaxSupp.rows; i++)
{
for (j = 0; j<nonMaxSupp.cols; j++)
{
EdgeMat.at<uchar>(i,j) = nonMaxSupp.at<uchar>(i,j);
if(EdgeMat.at<uchar>(i,j) > high)
EdgeMat.at<uchar>(i,j) = 255;
else if(EdgeMat.at<uchar>(i,j) < low)
EdgeMat.at<uchar>(i,j) = 0;
else
{
bool anyHigh = false;
bool anyBetween = false;
//for neighbouring pixels
for (int x=i-1; x < i+2; x++)
{
for (int y = j-1; y<j+2; y++)
{
if(x <= 0 || y <= 0 || x > EdgeMat.rows || y > EdgeMat.cols) //Out of bounds
continue;
else
{
if(EdgeMat.at<uchar>(x,y) > high)
{
EdgeMat.at<uchar>(i,j) = 255;
anyHigh = true;
break;
}
else if(EdgeMat.at<uchar>(x,y) <= high && EdgeMat.at<uchar>(x,y) >= low)
anyBetween = true;
}
}
if(anyHigh)
break;
}
if(!anyHigh && anyBetween)
for (int x=i-2; x < i+3; x++)
{
for (int y = j-1; y<j+3; y++)
{
if(x < 0 || y < 0 || x > EdgeMat.rows || y > EdgeMat.cols) //Out of bounds
continue;
else
{
if(EdgeMat.at<uchar>(x,y) > high)
{
EdgeMat.at<uchar>(i,j) = 255;
anyHigh = true;
break;
}
}
}
if(anyHigh)
break;
}
if(!anyHigh)
EdgeMat.at<uchar>(i,j) = 0;
}
}
}
end = omp_get_wtime();
diff = end-start;
cout<<"\nparallel code time:"<<diff<<endl;
imshow("Hysterisis Thresholding",EdgeMat);
waitKey(0);
return 0;
}