Tutorial Laplace Operator

doc/tutorials/imgproc/imgtrans/laplace_operator/laplace_operator.markdown

 Laplace Operator {#tutorial_laplace_operator}
 ================
 
+@prev_tutorial{tutorial_sobel_derivatives}
+@next_tutorial{tutorial_canny_detector}
+
 Goal
 ----
 
 In this tutorial you will learn how to:
 
--   Use the OpenCV function @ref cv::Laplacian to implement a discrete analog of the *Laplacian
+-   Use the OpenCV function **Laplacian()** to implement a discrete analog of the *Laplacian
     operator*.
 
 Theory
@@ -37,7 +40,7 @@ Theory
 
 \f[Laplace(f) = \dfrac{\partial^{2} f}{\partial x^{2}} + \dfrac{\partial^{2} f}{\partial y^{2}}\f]
 
--#  The Laplacian operator is implemented in OpenCV by the function @ref cv::Laplacian . In fact,
+-#  The Laplacian operator is implemented in OpenCV by the function **Laplacian()** . In fact,
     since the Laplacian uses the gradient of images, it calls internally the *Sobel* operator to
     perform its computation.
 
@@ -50,25 +53,98 @@ Code
     -   Applies a Laplacian operator to the grayscale image and stores the output image
     -   Display the result in a window
 
+@add_toggle_cpp
 -#  The tutorial code's is shown lines below. You can also download it from
-    [here](https://github.com/opencv/opencv/tree/master/samples/cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp)
+    [here](https://raw.githubusercontent.com/opencv/opencv/master/samples/cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp)
     @include samples/cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp
+@end_toggle
+
+@add_toggle_java
+-#  The tutorial code's is shown lines below. You can also download it from
+    [here](https://raw.githubusercontent.com/opencv/opencv/master/samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java)
+    @include samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java
+@end_toggle
+
+@add_toggle_python
+-#  The tutorial code's is shown lines below. You can also download it from
+    [here](https://raw.githubusercontent.com/opencv/opencv/master/samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py)
+    @include samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py
+@end_toggle
 
 Explanation
 -----------
 
--#  Create some needed variables:
-    @snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp variables
--#  Loads the source image:
-    @snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp load
--#  Apply a Gaussian blur to reduce noise:
-    @snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp reduce_noise
--#  Convert the image to grayscale using @ref cv::cvtColor
-    @snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp convert_to_gray
--#  Apply the Laplacian operator to the grayscale image:
-    @snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp laplacian
-    where the arguments are:
+#### Declare variables
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp variables
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java variables
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py variables
+@end_toggle
+
+#### Load source image
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp load
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java load
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py load
+@end_toggle
+
+#### Reduce noise
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp reduce_noise
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java reduce_noise
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py reduce_noise
+@end_toggle
 
+#### Grayscale
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp convert_to_gray
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java convert_to_gray
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py convert_to_gray
+@end_toggle
+
+#### Laplacian operator
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp laplacian
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java laplacian
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py laplacian
+@end_toggle
+
+-   The arguments are:
     -   *src_gray*: The input image.
     -   *dst*: Destination (output) image
     -   *ddepth*: Depth of the destination image. Since our input is *CV_8U* we define *ddepth* =
@@ -77,10 +153,33 @@ Explanation
         this example.
     -   *scale*, *delta* and *BORDER_DEFAULT*: We leave them as default values.
 
--#  Convert the output from the Laplacian operator to a *CV_8U* image:
-    @snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp convert
--#  Display the result in a window:
-    @snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp display
+#### Convert output to a *CV_8U* image
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp convert
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java convert
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py convert
+@end_toggle
+
+#### Display the result
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp display
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java display
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py display
+@end_toggle
 
 Results
 -------

doc/tutorials/imgproc/table_of_content_imgproc.markdown

@@ -99,6 +99,8 @@ In this section you will learn about the image processing (manipulation) functio
 
 -   @subpage tutorial_laplace_operator
 
+    *Languages:* C++, Java, Python
+
     *Compatibility:* \> OpenCV 2.0
 
     *Author:* Ana Huamán

samples/cpp/tutorial_code/ImgTrans/Laplace_Demo.cpp

@@ -15,50 +15,53 @@ using namespace cv;
  */
 int main( int argc, char** argv )
 {
-  //![variables]
-  Mat src, src_gray, dst;
-  int kernel_size = 3;
-  int scale = 1;
-  int delta = 0;
-  int ddepth = CV_16S;
-  const char* window_name = "Laplace Demo";
-  //![variables]
+    //![variables]
+    // Declare the variables we are going to use
+    Mat src, src_gray, dst;
+    int kernel_size = 3;
+    int scale = 1;
+    int delta = 0;
+    int ddepth = CV_16S;
+    const char* window_name = "Laplace Demo";
+    //![variables]
 
-  //![load]
-  String imageName("../data/lena.jpg"); // by default
-  if (argc > 1)
-  {
-    imageName = argv[1];
-  }
-  src = imread( imageName, IMREAD_COLOR ); // Load an image
+    //![load]
+    const char* imageName = argc >=2 ? argv[1] : "../data/lena.jpg";
 
-  if( src.empty() )
-    { return -1; }
-  //![load]
+    src = imread( imageName, IMREAD_COLOR ); // Load an image
 
-  //![reduce_noise]
-  /// Reduce noise by blurring with a Gaussian filter
-  GaussianBlur( src, src, Size(3,3), 0, 0, BORDER_DEFAULT );
-  //![reduce_noise]
+    // Check if image is loaded fine
+    if(src.empty()){
+        printf(" Error opening image\n");
+        printf(" Program Arguments: [image_name -- default ../data/lena.jpg] \n");
+        return -1;
+    }
+    //![load]
 
-  //![convert_to_gray]
-  cvtColor( src, src_gray, COLOR_BGR2GRAY ); // Convert the image to grayscale
-  //![convert_to_gray]
+    //![reduce_noise]
+    // Reduce noise by blurring with a Gaussian filter ( kernel size = 3 )
+    GaussianBlur( src, src, Size(3, 3), 0, 0, BORDER_DEFAULT );
+    //![reduce_noise]
 
-  /// Apply Laplace function
-  Mat abs_dst;
-  //![laplacian]
-  Laplacian( src_gray, dst, ddepth, kernel_size, scale, delta, BORDER_DEFAULT );
-  //![laplacian]
+    //![convert_to_gray]
+    cvtColor( src, src_gray, COLOR_BGR2GRAY ); // Convert the image to grayscale
+    //![convert_to_gray]
 
-  //![convert]
-  convertScaleAbs( dst, abs_dst );
-  //![convert]
+    /// Apply Laplace function
+    Mat abs_dst;
+    //![laplacian]
+    Laplacian( src_gray, dst, ddepth, kernel_size, scale, delta, BORDER_DEFAULT );
+    //![laplacian]
 
-  //![display]
-  imshow( window_name, abs_dst );
-  waitKey(0);
-  //![display]
+    //![convert]
+    // converting back to CV_8U
+    convertScaleAbs( dst, abs_dst );
+    //![convert]
 
-  return 0;
+    //![display]
+    imshow( window_name, abs_dst );
+    waitKey(0);
+    //![display]
+
+    return 0;
 }

samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java

+/**
+ * @file LaplaceDemo.java
+ * @brief Sample code showing how to detect edges using the Laplace operator
+ */
+
+import org.opencv.core.*;
+import org.opencv.highgui.HighGui;
+import org.opencv.imgcodecs.Imgcodecs;
+import org.opencv.imgproc.Imgproc;
+
+class LaplaceDemoRun {
+
+    public void run(String[] args) {
+        //! [variables]
+        // Declare the variables we are going to use
+        Mat src, src_gray = new Mat(), dst = new Mat();
+        int kernel_size = 3;
+        int scale = 1;
+        int delta = 0;
+        int ddepth = CvType.CV_16S;
+        String window_name = "Laplace Demo";
+        //! [variables]
+
+        //! [load]
+        String imageName = ((args.length > 0) ? args[0] : "../data/lena.jpg");
+
+        src = Imgcodecs.imread(imageName, Imgcodecs.IMREAD_COLOR); // Load an image
+
+        // Check if image is loaded fine
+        if( src.empty() ) {
+            System.out.println("Error opening image");
+            System.out.println("Program Arguments: [image_name -- default ../data/lena.jpg] \n");
+            System.exit(-1);
+        }
+        //! [load]
+
+        //! [reduce_noise]
+        // Reduce noise by blurring with a Gaussian filter ( kernel size = 3 )
+        Imgproc.GaussianBlur( src, src, new Size(3, 3), 0, 0, Core.BORDER_DEFAULT );
+        //! [reduce_noise]
+
+        //! [convert_to_gray]
+        // Convert the image to grayscale
+        Imgproc.cvtColor( src, src_gray, Imgproc.COLOR_RGB2GRAY );
+        //! [convert_to_gray]
+
+        /// Apply Laplace function
+        Mat abs_dst = new Mat();
+        //! [laplacian]
+        Imgproc.Laplacian( src_gray, dst, ddepth, kernel_size, scale, delta, Core.BORDER_DEFAULT );
+        //! [laplacian]
+
+        //! [convert]
+        // converting back to CV_8U
+        Core.convertScaleAbs( dst, abs_dst );
+        //! [convert]
+
+        //! [display]
+        HighGui.imshow( window_name, abs_dst );
+        HighGui.waitKey(0);
+        //! [display]
+
+        System.exit(0);
+    }
+}
+
+public class LaplaceDemo {
+    public static void main(String[] args) {
+        // Load the native library.
+        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
+        new LaplaceDemoRun().run(args);
+    }
+}

samples/python/tutorial_code/ImgTrans/LaPlace/laplace_demo.py

+"""
+@file laplace_demo.py
+@brief Sample code showing how to detect edges using the Laplace operator
+"""
+import sys
+import cv2
+
+def main(argv):
+    # [variables]
+    # Declare the variables we are going to use
+    ddepth = cv2.CV_16S
+    kernel_size = 3
+    window_name = "Laplace Demo"
+    # [variables]
+
+    # [load]
+    imageName = argv[0] if len(argv) > 0 else "../data/lena.jpg"
+
+    src = cv2.imread(imageName, cv2.IMREAD_COLOR) # Load an image
+
+    # Check if image is loaded fine
+    if src is None:
+        print ('Error opening image')
+        print ('Program Arguments: [image_name -- default ../data/lena.jpg]')
+        return -1
+    # [load]
+
+    # [reduce_noise]
+    # Remove noise by blurring with a Gaussian filter
+    src = cv2.GaussianBlur(src, (3, 3), 0)
+    # [reduce_noise]
+
+    # [convert_to_gray]
+    # Convert the image to grayscale
+    src_gray = cv2.cvtColor(src, cv2.COLOR_BGR2GRAY)
+    # [convert_to_gray]
+
+    # Create Window
+    cv2.namedWindow(window_name, cv2.WINDOW_AUTOSIZE)
+
+    # [laplacian]
+    # Apply Laplace function
+    dst = cv2.Laplacian(src_gray, ddepth, kernel_size)
+    # [laplacian]
+
+    # [convert]
+    # converting back to uint8
+    abs_dst = cv2.convertScaleAbs(dst)
+    # [convert]
+
+    # [display]
+    cv2.imshow(window_name, abs_dst)
+    cv2.waitKey(0)
+    # [display]
+
+    return 0
+
+if __name__ == "__main__":
+    main(sys.argv[1:])