update cpp samples and tutorials

samples/cpp/lsd_lines.cpp

@@ -1,11 +1,8 @@
 #include <iostream>
-#include <string>
 
-#include "opencv2/core/core.hpp"
-#include "opencv2/core/utility.hpp"
-#include "opencv2/imgproc/imgproc.hpp"
+#include "opencv2/imgproc.hpp"
 #include "opencv2/imgcodecs.hpp"
-#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/highgui.hpp"
 
 using namespace std;
 using namespace cv;
@@ -23,6 +20,9 @@ int main(int argc, char** argv)
 
     Mat image = imread(in, IMREAD_GRAYSCALE);
 
+    if( image.empty() )
+    { return -1; }
+
 #if 0
     Canny(image, image, 50, 200, 3); // Apply canny edge
 #endif