add default file to load in case sample was run without command line arguments

samples/gpu/farneback_optical_flow.cpp

@@ -44,8 +44,8 @@ static void colorizeFlow(const Mat &u, const Mat &v, Mat &dst)
 int main(int argc, char **argv)
 {
     CommandLineParser cmd(argc, argv,
-            "{ l left  | | specify left image }"
-            "{ r right | | specify right image }"
+            "{ l left  | ../data/basketball1.png | specify left image }"
+            "{ r right | ../data/basketball2.png | specify right image }"
             "{ h help  | | print help message }");
 
     cmd.about("Farneback's optical flow sample.");

samples/gpu/hog.cpp

@@ -115,11 +115,19 @@ int main(int argc, char** argv)
 {
     try
     {
+        Args args;
         if (argc < 2)
+        {
             printHelp();
-        Args args = Args::read(argc, argv);
-        if (help_showed)
-            return -1;
+            args.camera_id = 0;
+            args.src_is_camera = true;
+        }
+        else
+        {
+            args = Args::read(argc, argv);
+            if (help_showed)
+                return -1;
+        }
         App app(args);
         app.run();
     }

samples/gpu/opengl.cpp

@@ -14,6 +14,9 @@ int main()
     #define NOMINMAX 1
     #include <windows.h>
 #endif
+#if defined(_WIN64)
+    #include <windows.h>
+#endif
 
 #if defined(__APPLE__)
     #include <OpenGL/gl.h>
@@ -55,16 +58,19 @@ void draw(void* userdata)
 
 int main(int argc, char* argv[])
 {
+    string filename;
     if (argc < 2)
     {
         cout << "Usage: " << argv[0] << " image" << endl;
-        return -1;
+        filename = "../data/lena.jpg";
     }
+    else
+        filename = argv[1];
 
-    Mat img = imread(argv[1]);
+    Mat img = imread(filename);
     if (img.empty())
     {
-        cerr << "Can't open image " << argv[1] << endl;
+        cerr << "Can't open image " << filename << endl;
         return -1;
     }
 

samples/gpu/optical_flow.cpp

@@ -135,23 +135,30 @@ static void showFlow(const char* name, const GpuMat& d_flowx, const GpuMat& d_fl
 
 int main(int argc, const char* argv[])
 {
+    string filename1, filename2;
     if (argc < 3)
     {
-        cerr << "Usage : " << argv[0] << "<frame0> <frame1>" << endl;
-        return -1;
+        cerr << "Usage : " << argv[0] << " <frame0> <frame1>" << endl;
+        filename1 = "../data/basketball1.png";
+        filename2 = "../data/basketball2.png";
+    }
+    else
+    {
+        filename1 = argv[1];
+        filename2 = argv[2];
     }
 
-    Mat frame0 = imread(argv[1], IMREAD_GRAYSCALE);
-    Mat frame1 = imread(argv[2], IMREAD_GRAYSCALE);
+    Mat frame0 = imread(filename1, IMREAD_GRAYSCALE);
+    Mat frame1 = imread(filename2, IMREAD_GRAYSCALE);
 
     if (frame0.empty())
     {
-        cerr << "Can't open image ["  << argv[1] << "]" << endl;
+        cerr << "Can't open image ["  << filename1 << "]" << endl;
         return -1;
     }
     if (frame1.empty())
     {
-        cerr << "Can't open image ["  << argv[2] << "]" << endl;
+        cerr << "Can't open image ["  << filename2 << "]" << endl;
         return -1;
     }
 

samples/gpu/pyrlk_optical_flow.cpp

@@ -119,8 +119,8 @@ int main(int argc, const char* argv[])
 {
     const char* keys =
         "{ h             help   |       | print help message }"
-        "{ l             left   |       | specify left image }"
-        "{ r             right  |       | specify right image }"
+        "{ l             left   | ../data/pic1.png       | specify left image }"
+        "{ r             right  | ../data/pic2.png       | specify right image }"
         "{ gray                 |       | use grayscale sources [PyrLK Sparse] }"
         "{ win_size             | 21    | specify windows size [PyrLK] }"
         "{ max_level            | 3     | specify max level [PyrLK] }"