filename specified by arg

lines.cpp

@@ -2,7 +2,19 @@
 
 int main(int argc, char *argv[])
 {
-	cv::Mat img=cv::imread("files/masckera.png",CV_LOAD_IMAGE_GRAYSCALE);
+	char const *fname = "files/masckera.png";
+	if( 1<argc )
+		fname = argv[1];
+	if( 2<argc) {
+		std::cerr << "Too many arguments" << std::endl;
+		return EXIT_FAILURE;
+	}
+	cv::Mat img;
+	img=cv::imread(fname,CV_LOAD_IMAGE_GRAYSCALE);
+	if( img.empty() ) {
+		std::cerr << "Error opening image, aborting" << std::endl;
+		return EXIT_FAILURE;
+	}
 
 	std::vector< std::vector<cv::Point> > contours;
 	std::vector<cv::Vec4i> hierarchy;