#include "opencv2/core/utility.hpp"#include "opencv2/imgproc.hpp"#include "opencv2/imgcodecs.hpp"#include "opencv2/highgui.hpp"#include <stdio.h>using namespace cv;using namespace std;int edgeThresh = 1;Mat image, gray, edge, cedge;// define a trackbar callbackstatic void onTrackbar(int, void*){    /* Step one */    blur(gray, edge, Size(3,3));    // Run the edge detector on grayscale    Canny(edge, edge, edgeThresh, edgeThresh*3, 3);    cedge = Scalar::all(0);    /*     * Jeff --> the second parameter is mask.     */    image.copyTo(cedge, edge);    imshow("Edge map", cedge);}static void help(){    printf("\nThis sample demonstrates Canny edge detection\n"           "Call:\n"           "    /.edge [image_name -- Default is ../data/fruits.jpg]\n\n");}const char* keys ={    "{help h||}{@image |../data/fruits.jpg|input image name}"};int main( int argc, const char** argv ){    CommandLineParser parser(argc, argv, keys);    if (parser.has("help"))    {        help();        return 0;    }    string filename = parser.get<string>(0);    image = imread(filename, 1);    if(image.empty())    {        printf("Cannot read image file: %s\n", filename.c_str());        help();        return -1;    }    cedge.create(image.size(), image.type());    cvtColor(image, gray, COLOR_BGR2GRAY);    // Create a window    namedWindow("Edge map", 1);    // create a toolbar    createTrackbar("Canny threshold", "Edge map", &edgeThresh, 100, onTrackbar);    // Show the image    onTrackbar(0, 0);    // Wait for a key stroke; the same function arranges events processing    waitKey(0);    return 0;}