// Copyright 2015 Matt Heard
// http://mattheard.net
// matt@mattheard.net
// @mattheard

#include <opencv2/opencv.hpp>
#include <iostream>
#include <string>

using cv::Mat;

// TODO(mattheard): Implement me
Mat convertToGrey(const Mat &src) {
    return Mat();
}

int main(int argc, char **argv) {
    using std::string;
    const int expectedNumArgs = 2;
    if (argc != expectedNumArgs) {
        const string cmdName = "ConvertToGrey";
        const string argsDesc = " <Image_Path>";
        std::cout << "Usage: " << cmdName << argsDesc << std::endl;
        return -1;
    }
    const string filename = argv[1];
    const Mat srcImg = cv::imread(filename);
    if (!srcImg.data) {
        const string err = "No image data";
        std::cerr << err << std::cout;
        return -1;
    }
    const Mat greyImg = convertToGrey(srcImg);
    return 0;
}

// Copyright 2015 Matt Heard
// http://mattheard.net
// matt@mattheard.net
// @mattheard

#include <opencv2/opencv.hpp>
#include <iostream>
#include <string>

int main(int argc, char **argv) {
    using std::string;
    const int expectedNumArgs = 2;
    if (argc != expectedNumArgs) {
        const string cmdName = "ConvertToGrey";
        const string argsDesc = " <Image_Path>";
        std::cout << "Usage: " << cmdName << argsDesc << std::endl;
        return -1;
    }
    const string filename = argv[1];
    const cv::Mat img = cv::imread(filename);
    if (!img.data) {
        const string err = "No image data";
        std::cerr << err << std::cout;
        return -1;
    }
    return 0;
}

--- 
+++ 
@@ -6,6 +6,13 @@
 #include <opencv2/opencv.hpp>
 #include <iostream>
 #include <string>
+
+using cv::Mat;
+
+// TODO(mattheard): Implement me
+Mat convertToGrey(const Mat &src) {
+    return Mat();
+}
 
 int main(int argc, char **argv) {
     using std::string;
@@ -17,11 +24,12 @@
         return -1;
     }
     const string filename = argv[1];
-    const cv::Mat img = cv::imread(filename);
-    if (!img.data) {
+    const Mat srcImg = cv::imread(filename);
+    if (!srcImg.data) {
         const string err = "No image data";
         std::cerr << err << std::cout;
         return -1;
     }
+    const Mat greyImg = convertToGrey(srcImg);
     return 0;
 }
Add call to conversion fn
