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How to alter the brightness of a grey scale image?
The equalizeHist() method of the Imgproc class accepts a greyscale image and equalizes its histogram, which will, in turn, normalizes the brightness and increases the contrast of the given image. This method accepts two parameters −
A Mat object representing the source image (greyscale).
A Mat object to save the result.
Example
Following Java program reads a colored image as greyscale, saves it, normalizes the brightness and increases the contrast of the given image and saves it.
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.highgui.HighGui;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
public class HstExample {
public static void main(String args[]) {
//Loading the OpenCV core library
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
String input = "D://images//sunset.jpg";
//Reading the Image from the file
Mat source = Imgcodecs.imread(input, Imgcodecs.IMREAD_GRAYSCALE );
//Creating an empty matrix to store the result
Mat dst = new Mat(source.rows(),source.cols(),source.type());
Imgcodecs.imwrite("D://images//Grey_scale.jpg", source);
//Increasing the contrast
Imgproc.equalizeHist(source, dst);
//Writing the image
Imgcodecs.imwrite("D://images//increasing_contrast.jpg", dst);
HighGui.imshow("output image", dst);
}
}Greyscale image
Resultant image
Updated on: 09-Apr-2020
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