edge detection on digital images

I did this for the project proposal of D. Actually, there were no benefits for me to do this on digital images. I am working on point clouds which contains depth information, that is 3D image information.

However, it did not take me much time to do it. It was quite easy:

OpenCV is quite helpful on this aspect. I downloaded the source code from Canny Edge Detector tutorial

#include "opencv2/imgproc/imgproc.hpp"#include "opencv2/highgui/highgui.hpp"#include <stdlib.h>#include <stdio.h>using namespace cv;/// Global variablesMat src, src_gray;Mat dst, detected_edges;int edgeThresh = 1;int lowThreshold;int const max_lowThreshold = 100;int ratio = 3;int kernel_size = 3;char* window_name = "Edge Map";/** * @function CannyThreshold * @brief Trackbar callback - Canny thresholds input with a ratio 1:3 */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 argc, char** argv ){  /// Load an image  src = imread( argv[1] );  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, CV_BGR2GRAY );  /// Create a window  namedWindow( window_name, CV_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;  }

I made a ros package out of it by adding some dependencies in manifest.xml and executable in CMakeLists.txt.

Then I captured an photo of the object I wanted to detect with the toolbox a ROS packageperception_pcl : convert_pointcloud_to_image

rosrun pcl_ros convert_pointcloud_to_image input:=/camera/dth_registered/points output:=/my_image

So, I got a topic published with image data, and then images could be generated by subscribing to the topic and right click on the image GUI. EASY!

rosrun image_view image_view image:=/my_image