Java | Converting an Image into Grayscale using cvtColor()

To convert a color image to Grayscale image using OpenCV, we read the image into BufferedImage and convert it into Mat Object.

Syntax:
File input = new File("digital_image_processing.jpg");
BufferedImage image = ImageIO.read(input);

To transform the image from RGB to Grayscale format by using method cvtColor() in the Imgproc class.

Syntax:
Imgproc.cvtColor(source mat, destination mat1, Imgproc.COLOR_RGB2GRAY);
Parameters: The method cvtColor() takes three parameters which are the source image matrix, the destination image matrix, and the color conversion type.

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// Java program to convert a color image to gray scale
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
  
public class GeeksforGeeks {
    public static void main(String args[]) throws Exception
    {
  
        // To load  OpenCV core library
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        String input = "C:/opencv/GeeksforGeeks.jpg";
  
        // To Read the image
        Mat source = Imgcodecs.imread(input);
  
        // Creating the empty destination matrix
        Mat destination = new Mat();
  
        // Converting the image to gray scale and 
        // saving it in the dst matrix
        Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2GRAY);
  
        // Writing the image
        Imgcodecs.imwrite("C:/opencv/GeeksforGeeks.jpg", destination);
        System.out.println("The image is successfully to Grayscale");
    }
}

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Output :




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