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
\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.
- 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* =
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
-------
- @subpage tutorial_laplace_operator
+ *Languages:* C++, Java, Python
+
*Compatibility:* \> OpenCV 2.0
*Author:* Ana Huamán
*/
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;
}
--- /dev/null
+/**
+ * @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);
+ }
+}
--- /dev/null
+"""
+@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:])
projects / platform / upstream / opencv.git / commitdiff