Graceful failing on missing data

DescriptorManager.cpp

@@ -4,13 +4,15 @@ DescriptorManager::DescriptorManager() {} //don't use this
 DescriptorManager::DescriptorManager(const fs::path & image_path) {
 	img_path = image_path;
 	if (!fs::exists(img_path)) {
-		cout << "Error. Data folder not found." << endl;
-		return; //No data: giving up.
+		throw std::invalid_argument("Data missing");
 	}
 	numImages = std::count_if(
 		fs::directory_iterator(img_path),
 		fs::directory_iterator(),
 		static_cast<bool(*)(const fs::path&)>(fs::is_regular_file));
+	if (numImages <= 0) {
+		throw std::invalid_argument("Data missing");
+	}
 	current_image = NULL;
 	//Manual definitions.. SAD!
 	descriptor_types[7] = new DCTMedian();

Mutation.h

@@ -125,8 +125,12 @@ public:
 class Watermark : public Mutation {
 public:
 	Watermark() {
-		watermark = new Image;
-		watermark->read("watermark.png");
+		try {
+			watermark = new Image;
+			watermark->read("watermark.png");
+		} catch ( Magick::ErrorFileOpen &error ) {
+			watermark = new Image("40x40", "white");
+		}
 	}
 	Image * getMutated(Image* img) {
 		Image* mut = new Image(*img);

main.cpp

@@ -6,27 +6,33 @@
 #include <boost/filesystem/fstream.hpp>
 #include <string>*/
 
+#include <exception>
 #include "DescriptorManager.h"
 #include <boost/filesystem.hpp>
 #include <Magick++.h>
-using namespace std;
 using namespace Magick;
 
 enum method {avg_color, num_color, median, sobel, pearson, threshold, dct_pearson, dct_median};
 
 int main(int argc, char **argv) {
-	string imagename = "im3102.jpg";
+	std::string imagename = "im3102.jpg";
 	int method = method::median;
 	if (argc > 2) {
 		method = atoi(argv[2]);
 		imagename = argv[1];
 	}
 	else {
-		cout << "Usage: " << endl << argv[0] << " [fileName] [methodIndex]" << endl;
-		cout << "Continuing.." << endl;
+		std::cout << "Usage: " << std::endl << argv[0] << " [fileName] [methodIndex]" << std::endl;
+		std::cout << "Continuing.." << std::endl;
 	}
 	InitializeMagick(*argv);
-	DescriptorManager* manager = new DescriptorManager("data"); 
+	DescriptorManager* manager;
+	try {
+		manager = new DescriptorManager("data"); 
+	} catch (const std::exception& e) {
+		std::cout << "Creating manager failed: " << e.what() << std::endl;
+		return -1;
+	}
 	manager->Init();/*
 	manager->rankImages(imagename, method);
 	manager->outputRank(imagename, method);