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In this chapter we learn apply two very common morphology operators:Dilation and Erosion.
We use OpenCV function erode and dilate. They can be found under Imgproc package. Its syntax is given below −
Imgproc.erode(source, destination, element); Imgproc.dilate(source, destination, element);
The parameters are described below −
| Sr.No. | Parameter & Description |
|---|---|
| 1 |
source It is Source image. |
| 2 |
destination It is destination image. |
| 3 |
element It is a structuring element used for erosion and dilation, if element=Mat(), a 3 x 3 rectangular structuring element is used. |
Apart from erode() and dilate() methods, there are other methods provided by the Imgproc class. They are described briefly −
| Sr.No. | Method & Description |
|---|---|
| 1 |
cvtColor(Mat src, Mat dst, int code, int dstCn) It converts an image from one color space to another. |
| 2 |
dilate(Mat src, Mat dst, Mat kernel) It dilates an image by using a specific structuring element. |
| 3 |
equalizeHist(Mat src, Mat dst) It equalizes the histogram of a grayscale image. |
| 4 |
filter2D(Mat src, Mat dst, int depth, Mat kernel, Point anchor, double delta) It convolves an image with the kernel. |
| 5 |
GaussianBlur(Mat src, Mat dst, Size ksize, double sigmaX) It blurs an image using a Gaussian filter. |
| 6 |
integral(Mat src, Mat sum) It calculates the integral of an image. |
Example
The following example demonstrates the use of Imgproc class to perform erosion and dilation on an image −
import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.highgui.Highgui;
import org.opencv.imgproc.Imgproc;
public class main {
public static void main( String[] args ) {
try{
System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
Mat source = Highgui.imread("digital_image_processing.jpg", Highgui.CV_LOAD_IMAGE_COLOR);
Mat destination = new Mat(source.rows(),source.cols(),source.type());
destination = source;
int erosion_size = 5;
int dilation_size = 5;
Mat element = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(2*erosion_size + 1, 2*erosion_size+1));
Imgproc.erode(source, destination, element);
Highgui.imwrite("erosion.jpg", destination);
source = Highgui.imread("digital_image_processing.jpg", Highgui.CV_LOAD_IMAGE_COLOR);
destination = source;
Mat element1 = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(2*dilation_size + 1, 2*dilation_size+1));
Imgproc.dilate(source, destination, element1);
Highgui.imwrite("dilation.jpg", destination);
} catch (Exception e) {
System.out.println("error:" + e.getMessage());
}
}
}
Output
When you execute the given code, the following output is seen −
Original Image
On the above original image, some erosion and dilation operations have been performed which have been shown in the output below −
Erosion
Dilation
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