converted some OpenCV C samples to C++

samples/cpp/edge.cpp

@@ -0,0 +1,52 @@
+#include <opencv2/imgproc/imgproc.hpp>
+#include <opencv2/highgui/highgui.hpp>
+
+#include <iostream>
+
+using namespace cv;
+using namespace std;
+
+int edgeThresh = 1;
+Mat image, gray, edge, cedge;
+
+// define a trackbar callback
+void onTrackbar(int, void*)
+{
+    blur(gray, edge, Size(3,3));
+
+    // Run the edge detector on grayscale
+    Canny(edge, edge, edgeThresh, edgeThresh*3, 3);
+    cedge = Scalar::all(0);
+    
+    image.copyTo(cedge, edge);
+    imshow("Edge map", cedge);
+}
+
+int main( int argc, char** argv )
+{
+    char* filename = argc == 2 ? argv[1] : (char*)"fruits.jpg";
+
+    image = imread(filename, 1);
+    if(image.empty())
+    {
+        cout << "Usage: edge <image_name>" << endl;
+        return -1;
+    }
+
+    cedge.create(image.size(), image.type());
+    cvtColor(image, gray, CV_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;
+}