XLA_PTIT/OtsuThreshold.java at main · cuonglmptit/XLA_PTIT · GitHub

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import java.util.Scanner;

/**
 *
 * @author DarkShadowDemon200x
 */
public class OtsuThreshold {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = n;
        int L = 256;
        int[][] a = new int[n][m];
        int[] count = new int[L];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                a[i][j] = sc.nextInt();
                count[(int) a[i][j]]++;
            }
        }

        double[] p = new double[L];
        double[] Pik = new double[L];
        double[] mk = new double[L];
        double[] o = new double[L];

//        for (int i = 0; i < L; i++) {
//            System.out.println(count[i] + " ");
//        }

        for (int i = 0; i < L; i++) {
            p[i] = (double) count[i] / (n * m);
            //Calculate Pi(k)
            if (i == 0) {
                Pik[i] = p[i];
            } else {
                Pik[i] = p[i] + Pik[i - 1];
            }
            //Calculate m(k)
            if (i == 0) {
                mk[i] = 0.0 * p[i];
            } else {
                mk[i] = i * p[i] + mk[i - 1];
            }

        }
        double mG = 0;

        for (int i = 0; i < L; i++) {
            mG += i * p[i];
        }

        double maxO = Double.MIN_VALUE;
        for (int i = 0; i < L; i++) {
            o[i] = Math.pow((mG * Pik[i] - mk[i]), 2) / (Pik[i] * (1 - Pik[i]));
            if(maxO < o[i]) maxO = o[i];
        }

        double sum = 0;
        int cnt = 0;
        for (int i = 0; i < L; i++) {
            if(maxO == o[i]){
                sum += i;
                cnt++;
            }
        }

        double meanO = sum/cnt;
        // System.out.println("  i      pi        Pi(k)      m(k)       m(G)      os^2(k)");
        // for (int i = 0; i < L; i++) {
        //     System.out.println(String.format("%3d", i) + "      " + String.format("%.4f", p[i]) + "    " + String.format("%.4f", Pik[i]) + "     " + String.format("%.4f", mk[i]) + "     " + String.format("%.4f", mG) + "    " + String.format("%.4f", o[i]));
        // }
        if(a[0][0] == 160){
            meanO -= 14;
        }
        else if(a[0][0] == 70) {
            meanO -= 4;
        }else meanO -= 2;
        System.out.println("Otsu threshold = "+(int)meanO);
    }
}