[OpenCV] Canny Detector

Canny Detector.cpp

/**
 Theme: Canny Detector
 IDE: Xcode 7, OSX 10.10
 Language: C++, OpenCV 2.4.12
 Date: 104/12/04
 Author: HappyMan
 Blog: http://cg2010studio.wordpress.com/
 */

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdlib.h>
#include <stdio.h>

using namespace cv;

/// Global variables

Mat src, src_gray;
Mat dst, detected_edges;

int edgeThresh = 1;
int lowThreshold;
int const max_lowThreshold = 100;
int ratio = 3;
int kernel_size = 3;
const char* window_name = "Happy Edge Map";

/**
 * @function CannyThreshold
 * @brief Trackbar callback - Canny thresholds input with a ratio 1:3
 */
static void CannyThreshold(int, void*)
{
    /// Reduce noise with a kernel 3x3
    blur(src_gray, detected_edges, Size(3,3));
    
    /// Canny detector
    Canny(detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size);
    
    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);
    
    src.copyTo(dst, detected_edges);
    imshow(window_name, dst);
}

/**
 * @function main
 */
int main(int, char** argv)
{
    /// Load an image
    src = imread("fang.jpg", CV_LOAD_IMAGE_COLOR);
    
    if(!src.data)
    { return -1; }
    
    /// Create a matrix of the same type and size as src (for dst)
    dst.create(src.size(), src.type());
    
    /// Convert the image to grayscale
    cvtColor(src, src_gray, COLOR_BGR2GRAY);
    
    /// Create a window
    namedWindow(window_name, WINDOW_AUTOSIZE);
    
    /// Create a Trackbar for user to enter threshold
    createTrackbar("Min Threshold:", window_name, &lowThreshold, max_lowThreshold, CannyThreshold);
    
    /// Show the image
    CannyThreshold(0, 0);
    
    /// Wait until user exit program by pressing a key
    waitKey(0);
    
    return 0;
}