Java DIP – Enhancing Image Contrast

We use the OpenCV function equalizeHist() method. It can be found under Imgproc package. Its syntax is given below − Imgproc.equalizeHist(source, destination); The parameters are described below − Sr.No. Parameter & Description 1 Source It is 8-bit single channel source image. 2 Destination It is the destination image. Apart from the equalizeHist() method, 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 ddepth, 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 enhance contrast of an image − import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.highgui.Highgui; import org.opencv.imgproc.Imgproc; public class Main { static int width; static int height; static double alpha = 2; static double beta = 50; public static void main( String[] args ) { try { System.loadLibrary( Core.NATIVE_LIBRARY_NAME ); Mat source = Highgui.imread("grayscale.jpg", Highgui.CV_LOAD_IMAGE_GRAYSCALE); Mat destination = new Mat(source.rows(),source.cols(),source.type()); Imgproc.equalizeHist(source, destination); Highgui.imwrite("contrast.jpg", destination); } catch (Exception e) { System.out.println("error: " + e.getMessage()); } } }Output When you execute the given code, the following output is seen −