Fixed compilation warnings in samples:

- use per-module includes instead of "opencv.hpp"
- unused function warnings
- undefined macro warning

samples/cpp/application_trace.cpp

 /* OpenCV Application Tracing support demo. */
 #include <iostream>
 
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
 #include <opencv2/core/utils/trace.hpp>
 
 using namespace cv;

samples/cpp/autofocus.cpp

@@ -28,7 +28,9 @@
 #include <cstdio>
 #include <iostream>
 #include <algorithm>
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
 
 using namespace std;
 using namespace cv;

samples/cpp/detect_blob.cpp

-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/features2d.hpp>
 #include <vector>
 #include <map>
 #include <iostream>

samples/cpp/detect_mser.cpp

-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/features2d.hpp>
 #include "opencv2/core/opengl.hpp"
-#include "opencv2/cvconfig.h"
 
 #include <vector>
 #include <map>

samples/cpp/matchmethod_orb_akaze_brisk.cpp

-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/features2d.hpp>
+#include <opencv2/highgui.hpp>
 #include <vector>
 #include <iostream>
 

samples/cpp/train_svmsgd.cpp

-#include <opencv2/opencv.hpp>
+#include "opencv2/core.hpp"
 #include "opencv2/video/tracking.hpp"
-#include "opencv2/imgproc/imgproc.hpp"
-#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/imgproc.hpp"
+#include "opencv2/highgui.hpp"
+#include "opencv2/ml.hpp"
 
 using namespace cv;
 using namespace cv::ml;

samples/cpp/travelsalesman.cpp

-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/ml.hpp>
 
 using namespace cv;
 

samples/cpp/tutorial_code/ImgProc/morph_lines_detection/Morphology_3.cpp

@@ -4,7 +4,10 @@
  * @author OpenCV team
  */
 
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+#include <iostream>
 
 void show_wait_destroy(const char* winname, cv::Mat img);
 

samples/cpp/tutorial_code/ImgTrans/imageSegmentation.cpp

@@ -4,7 +4,9 @@
  * @author OpenCV Team
  */
 
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
 #include <iostream>
 
 using namespace std;

samples/cpp/tutorial_code/calib3d/camera_calibration/camera_calibration.cpp

@@ -245,11 +245,6 @@ static inline void read(const FileNode& node, Settings& x, const Settings& defau
         x.read(node);
 }
 
-static inline void write(FileStorage& fs, const String&, const Settings& s )
-{
-    s.write(fs);
-}
-
 enum { DETECTION = 0, CAPTURING = 1, CALIBRATED = 2 };
 
 bool runCalibrationAndSave(Settings& s, Size imageSize, Mat&  cameraMatrix, Mat& distCoeffs,

samples/cpp/tutorial_code/calib3d/real_time_pose_estimation/src/CsvWriter.h

@@ -3,7 +3,7 @@
 
 #include <iostream>
 #include <fstream>
-#include <opencv2/core/core.hpp>
+#include <opencv2/core.hpp>
 #include "Utils.h"
 
 using namespace std;

samples/cpp/tutorial_code/calib3d/real_time_pose_estimation/src/ModelRegistration.h

@@ -9,7 +9,7 @@
 #define MODELREGISTRATION_H_
 
 #include <iostream>
-#include <opencv2/core/core.hpp>
+#include <opencv2/core.hpp>
 
 class ModelRegistration
 {

samples/cpp/tutorial_code/features2D/AKAZE_tracking/planar_tracking.cpp

 #include <opencv2/features2d.hpp>
 #include <opencv2/videoio.hpp>
-#include <opencv2/opencv.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/calib3d.hpp>
 #include <opencv2/highgui.hpp>      //for imshow
 #include <vector>
 #include <iostream>

samples/cpp/tutorial_code/features2D/Homography/decompose_homography.cpp

 #include <iostream>
 #include <opencv2/opencv_modules.hpp>
 #ifdef HAVE_OPENCV_ARUCO
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/videoio.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/calib3d.hpp>
 #include <opencv2/aruco.hpp>
 
 using namespace std;

samples/cpp/tutorial_code/features2D/Homography/homography_from_camera_displacement.cpp

 #include <iostream>
 #include <opencv2/opencv_modules.hpp>
 #ifdef HAVE_OPENCV_ARUCO
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/calib3d.hpp>
 #include <opencv2/aruco.hpp>
 
 using namespace std;

samples/cpp/tutorial_code/features2D/Homography/panorama_stitching_rotating_camera.cpp

 #include <iostream>
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/stitching.hpp>
 
 using namespace std;
 using namespace cv;

samples/cpp/tutorial_code/features2D/Homography/perspective_correction.cpp

 #include <iostream>
 #include <opencv2/opencv_modules.hpp>
 #ifdef HAVE_OPENCV_ARUCO
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/calib3d.hpp>
+#include <opencv2/highgui.hpp>
 #include <opencv2/aruco.hpp>
 
 using namespace std;
@@ -17,32 +20,6 @@ Scalar randomColor( RNG& rng )
   return Scalar( icolor & 255, (icolor >> 8) & 255, (icolor >> 16) & 255 );
 }
 
-void calcChessboardCorners(Size boardSize, float squareSize, vector<Point3f>& corners, Pattern patternType = CHESSBOARD)
-{
-    corners.resize(0);
-
-    switch (patternType)
-    {
-    case CHESSBOARD:
-    case CIRCLES_GRID:
-        for( int i = 0; i < boardSize.height; i++ )
-            for( int j = 0; j < boardSize.width; j++ )
-                corners.push_back(Point3f(float(j*squareSize),
-                                          float(i*squareSize), 0));
-        break;
-
-    case ASYMMETRIC_CIRCLES_GRID:
-        for( int i = 0; i < boardSize.height; i++ )
-            for( int j = 0; j < boardSize.width; j++ )
-                corners.push_back(Point3f(float((2*j + i % 2)*squareSize),
-                                          float(i*squareSize), 0));
-        break;
-
-    default:
-        CV_Error(Error::StsBadArg, "Unknown pattern type\n");
-    }
-}
-
 void perspectiveCorrection(const string &img1Path, const string &img2Path, const Size &patternSize, RNG &rng)
 {
     Mat img1 = imread(img1Path);

samples/cpp/tutorial_code/features2D/Homography/pose_from_homography.cpp

 #include <iostream>
 #include <opencv2/opencv_modules.hpp>
 #ifdef HAVE_OPENCV_ARUCO
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/calib3d.hpp>
+#include <opencv2/highgui.hpp>
 #include <opencv2/aruco.hpp>
 
 using namespace std;

samples/cpp/tutorial_code/snippets/core_various.cpp

-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/features2d.hpp>
 
 using namespace std;
 using namespace cv;

samples/cpp/tutorial_code/snippets/imgcodecs_imwrite.cpp

-#include <opencv2/opencv.hpp>
+#include <opencv2/imgcodecs.hpp>
 
 using namespace cv;
 using namespace std;

samples/cpp/tutorial_code/viz/histo3D.cpp

-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
 #include <iostream>
 
 using namespace std;
@@ -6,6 +8,8 @@ using namespace cv;
 
 #ifdef HAVE_OPENCV_VIZ
 
+#include <opencv2/viz.hpp>
+
 const String keys =
 "{Aide h usage ? help  |     | print this message   }"
 "{@arg1                |     | Full path to color imag (3 channels)}"

samples/cpp/tutorial_code/xfeatures2D/LATCH_match.cpp

@@ -4,10 +4,12 @@
 
 #ifdef HAVE_OPENCV_XFEATURES2D
 
+#include <opencv2/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
 #include <opencv2/features2d.hpp>
 #include <opencv2/xfeatures2d.hpp>
 #include <opencv2/imgcodecs.hpp>
-#include <opencv2/opencv.hpp>
 #include <vector>
 
 // If you find this code useful, please add a reference to the following paper in your work:

samples/cpp/videocapture_basic.cpp

@@ -5,7 +5,9 @@
   @date Aug 24, 2016
 */
 
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/videoio.hpp>
+#include <opencv2/highgui.hpp>
 #include <iostream>
 #include <stdio.h>
 
@@ -49,4 +51,4 @@ int main(int, char**)
     }
     // the camera will be deinitialized automatically in VideoCapture destructor
     return 0;
-}
+}
\ No newline at end of file

samples/cpp/videowriter_basic.cpp

@@ -5,7 +5,9 @@
   @date Aug 24, 2016
 */
 
-#include <opencv2/opencv.hpp>
+#include <opencv2/core.hpp>
+#include <opencv2/videoio.hpp>
+#include <opencv2/highgui.hpp>
 #include <iostream>
 #include <stdio.h>
 
@@ -62,4 +64,4 @@ int main(int, char**)
     }
     // the videofile will be closed and released automatically in VideoWriter destructor
     return 0;
-}
+}
\ No newline at end of file

samples/opencl/opencl-opencv-interop.cpp

@@ -16,7 +16,7 @@
 
 #define CL_USE_DEPRECATED_OPENCL_2_0_APIS // eliminate build warning
 
-#if __APPLE__
+#ifdef __APPLE__
 #include <OpenCL/cl.h>
 #else
 #include <CL/cl.h>