OpenCV  4.5.1
Open Source Computer Vision
samples/cpp/edge.cpp

This program demonstrates usage of the Canny edge detector

Check the corresponding tutorial for more details

#include <stdio.h>
using namespace cv;
using namespace std;
int edgeThresh = 1;
int edgeThreshScharr=1;
Mat image, gray, blurImage, edge1, edge2, cedge;
const char* window_name1 = "Edge map : Canny default (Sobel gradient)";
const char* window_name2 = "Edge map : Canny with custom gradient (Scharr)";
// define a trackbar callback
static void onTrackbar(int, void*)
{
blur(gray, blurImage, Size(3,3));
// Run the edge detector on grayscale
Canny(blurImage, edge1, edgeThresh, edgeThresh*3, 3);
cedge = Scalar::all(0);
image.copyTo(cedge, edge1);
imshow(window_name1, cedge);
Mat dx,dy;
Scharr(blurImage,dx,CV_16S,1,0);
Scharr(blurImage,dy,CV_16S,0,1);
Canny( dx,dy, edge2, edgeThreshScharr, edgeThreshScharr*3 );
cedge = Scalar::all(0);
image.copyTo(cedge, edge2);
imshow(window_name2, cedge);
}
static void help(const char** argv)
{
printf("\nThis sample demonstrates Canny edge detection\n"
"Call:\n"
" %s [image_name -- Default is fruits.jpg]\n\n", argv[0]);
}
const char* keys =
{
"{help h||}{@image |fruits.jpg|input image name}"
};
int main( int argc, const char** argv )
{
help(argv);
CommandLineParser parser(argc, argv, keys);
string filename = parser.get<string>(0);
image = imread(samples::findFile(filename), IMREAD_COLOR);
if(image.empty())
{
printf("Cannot read image file: %s\n", filename.c_str());
help(argv);
return -1;
}
cedge.create(image.size(), image.type());
cvtColor(image, gray, COLOR_BGR2GRAY);
// Create a window
namedWindow(window_name1, 1);
namedWindow(window_name2, 1);
// create a toolbar
createTrackbar("Canny threshold default", window_name1, &edgeThresh, 100, onTrackbar);
createTrackbar("Canny threshold Scharr", window_name2, &edgeThreshScharr, 400, onTrackbar);
// Show the image
onTrackbar(0, 0);
// Wait for a key stroke; the same function arranges events processing
waitKey(0);
return 0;
}
cv::imread
CV_EXPORTS_W Mat imread(const String &filename, int flags=IMREAD_COLOR)
Loads an image from a file.
cv::Scalar_< double >::all
static Scalar_< double > all(double v0)
returns a scalar with all elements set to v0
cv::cvtColor
void cvtColor(InputArray src, OutputArray dst, int code, int dstCn=0)
Converts an image from one color space to another.
cv::samples::findFile
cv::String findFile(const cv::String &relative_path, bool required=true, bool silentMode=false)
Try to find requested data file.
cv::waitKey
int waitKey(int delay=0)
Waits for a pressed key.
cv::Canny
void Canny(InputArray image, OutputArray edges, double threshold1, double threshold2, int apertureSize=3, bool L2gradient=false)
Finds edges in an image using the Canny algorithm .
highgui.hpp
cv::namedWindow
void namedWindow(const String &winname, int flags=WINDOW_AUTOSIZE)
Creates a window.
cv::Size
Size2i Size
Definition: types.hpp:347
imgcodecs.hpp
cv::imshow
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.
cv::Scharr
void Scharr(InputArray src, OutputArray dst, int ddepth, int dx, int dy, double scale=1, double delta=0, int borderType=BORDER_DEFAULT)
Calculates the first x- or y- image derivative using Scharr operator.
cv::blur
void blur(InputArray src, OutputArray dst, Size ksize, Point anchor=Point(-1,-1), int borderType=BORDER_DEFAULT)
Blurs an image using the normalized box filter.
cv::Mat
n-dimensional dense array class
Definition: mat.hpp:798
CV_16S
#define CV_16S
Definition: interface.h:76
cv::Mat::copyTo
void copyTo(OutputArray m) const
Copies the matrix to another one.
cv::CommandLineParser
Designed for command line parsing.
Definition: utility.hpp:789
cv::IMREAD_COLOR
@ IMREAD_COLOR
If set, always convert image to the 3 channel BGR color image.
Definition: imgcodecs.hpp:72
cv::COLOR_BGR2GRAY
@ COLOR_BGR2GRAY
convert between RGB/BGR and grayscale, color conversions
Definition: imgproc.hpp:546
cv::createTrackbar
int createTrackbar(const String &trackbarname, const String &winname, int *value, int count, TrackbarCallback onChange=0, void *userdata=0)
Creates a trackbar and attaches it to the specified window.
cv
"black box" representation of the file storage associated with a file on disk.
Definition: affine.hpp:52
imgproc.hpp
cv::Mat::create
void create(int rows, int cols, int type)
Allocates new array data if needed.
utility.hpp