Add Java and Python code for the following tutorials:

- Changing the contrast and brightness of an image!
      - Operations with images

samples/java/tutorial_code/core/mat_operations/MatOperations.java

@@ -0,0 +1,130 @@
+import java.util.Arrays;
+
+import org.opencv.core.Core;
+import org.opencv.core.Core.MinMaxLocResult;
+import org.opencv.core.CvType;
+import org.opencv.core.Mat;
+import org.opencv.core.Rect;
+import org.opencv.highgui.HighGui;
+import org.opencv.imgcodecs.Imgcodecs;
+import org.opencv.imgproc.Imgproc;
+
+public class MatOperations {
+    @SuppressWarnings("unused")
+    public static void main(String[] args) {
+        /*  Snippet code for Operations with images tutorial (not intended to be run) */
+
+        // Load the native OpenCV library
+        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
+
+        String filename = "";
+        // Input/Output
+        {
+            //! [Load an image from a file]
+            Mat img = Imgcodecs.imread(filename);
+            //! [Load an image from a file]
+        }
+        {
+            //! [Load an image from a file in grayscale]
+            Mat img = Imgcodecs.imread(filename, Imgcodecs.IMREAD_GRAYSCALE);
+            //! [Load an image from a file in grayscale]
+        }
+        {
+            Mat img = new Mat(4, 4, CvType.CV_8U);
+            //! [Save image]
+            Imgcodecs.imwrite(filename, img);
+            //! [Save image]
+        }
+        // Accessing pixel intensity values
+        {
+            Mat img = new Mat(4, 4, CvType.CV_8U);
+            int y = 0, x = 0;
+            {
+                //! [Pixel access 1]
+                byte[] imgData = new byte[(int) (img.total() * img.channels())];
+                img.get(0, 0, imgData);
+                byte intensity = imgData[y * img.cols() + x];
+                //! [Pixel access 1]
+            }
+            {
+                //! [Pixel access 5]
+                byte[] imgData = new byte[(int) (img.total() * img.channels())];
+                imgData[y * img.cols() + x] = (byte) 128;
+                img.put(0, 0, imgData);
+                //! [Pixel access 5]
+            }
+
+        }
+        // Memory management and reference counting
+        {
+            //! [Reference counting 2]
+            Mat img = Imgcodecs.imread("image.jpg");
+            Mat img1 = img.clone();
+            //! [Reference counting 2]
+        }
+        {
+            //! [Reference counting 3]
+            Mat img = Imgcodecs.imread("image.jpg");
+            Mat sobelx = new Mat();
+            Imgproc.Sobel(img, sobelx, CvType.CV_32F, 1, 0);
+            //! [Reference counting 3]
+        }
+        // Primitive operations
+        {
+            Mat img = new Mat(400, 400, CvType.CV_8UC3);
+            {
+                //! [Set image to black]
+                byte[] imgData = new byte[(int) (img.total() * img.channels())];
+                Arrays.fill(imgData, (byte) 0);
+                img.put(0, 0, imgData);
+                //! [Set image to black]
+            }
+            {
+                //! [Select ROI]
+                Rect r = new Rect(10, 10, 100, 100);
+                Mat smallImg = img.submat(r);
+                //! [Select ROI]
+            }
+        }
+        {
+            //! [BGR to Gray]
+            Mat img = Imgcodecs.imread("image.jpg"); // loading a 8UC3 image
+            Mat grey = new Mat();
+            Imgproc.cvtColor(img, grey, Imgproc.COLOR_BGR2GRAY);
+            //! [BGR to Gray]
+        }
+        {
+            Mat dst = new Mat(), src = new Mat();
+            //! [Convert to CV_32F]
+            src.convertTo(dst, CvType.CV_32F);
+            //! [Convert to CV_32F]
+        }
+        // Visualizing images
+        {
+            //! [imshow 1]
+            Mat img = Imgcodecs.imread("image.jpg");
+            HighGui.namedWindow("image", HighGui.WINDOW_AUTOSIZE);
+            HighGui.imshow("image", img);
+            HighGui.waitKey();
+            //! [imshow 1]
+        }
+        {
+            //! [imshow 2]
+            Mat img = Imgcodecs.imread("image.jpg");
+            Mat grey = new Mat();
+            Imgproc.cvtColor(img, grey, Imgproc.COLOR_BGR2GRAY);
+            Mat sobelx = new Mat();
+            Imgproc.Sobel(grey, sobelx, CvType.CV_32F, 1, 0);
+            MinMaxLocResult res = Core.minMaxLoc(sobelx); // find minimum and maximum intensities
+            Mat draw = new Mat();
+            double maxVal = res.maxVal, minVal = res.minVal;
+            sobelx.convertTo(draw, CvType.CV_8U, 255.0 / (maxVal - minVal), -minVal * 255.0 / (maxVal - minVal));
+            HighGui.namedWindow("image", HighGui.WINDOW_AUTOSIZE);
+            HighGui.imshow("image", draw);
+            HighGui.waitKey();
+            //! [imshow 2]
+        }
+        System.exit(0);
+    }
+
+}