/*
 * #%L
 * Image processing operations for SciJava Ops.
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 *    this list of conditions and the following disclaimer.
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 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
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package org.scijava.ops.image.threshold;

// Ported from Antti Niemisto's HistThresh Matlab toolbox
//   Relicensed BSD 2-12-13

/**
 * Utility methods used by the various threshold methods.
 *
 * @author Barry DeZonia
 * @author Gabriel Landini
 */
public final class Thresholds {

	private Thresholds() {
		// NB: Prevent instantiation of utility class.
	}

	public static boolean bimodalTest(double[] y) {
        var len = y.length;
        var modes = 0;

		for (var k = 1; k < len - 1; k++) {
			if (y[k - 1] < y[k] && y[k + 1] < y[k]) {
				modes++;
				if (modes > 2) return false;
			}
		}
		return (modes == 2);
	}

	/**
	 * The partial sum A from C. A. Glasbey, "An analysis of histogram-based
	 * thresholding algorithms," CVGIP: Graphical Models and Image Processing,
	 * vol. 55, pp. 532-537, 1993.
	 */
	public static double A(long[] y, int j) {
		double x = 0;
		for (var i = 0; i <= j; i++)
			x += y[i];
		return x;
	}

	/**
	 * The partial sum B from C. A. Glasbey, "An analysis of histogram-based
	 * thresholding algorithms," CVGIP: Graphical Models and Image Processing,
	 * vol. 55, pp. 532-537, 1993.
	 */
	public static double B(long[] y, int j) {
		double x = 0;
		for (var i = 0; i <= j; i++)
			x += y[i] * i;
		return x;
	}

	/**
	 * The partial sum C from C. A. Glasbey, "An analysis of histogram-based
	 * thresholding algorithms," CVGIP: Graphical Models and Image Processing,
	 * vol. 55, pp. 532-537, 1993.
	 */
	public static double C(long[] y, int j) {
		double x = 0;
		for (var i = 0; i <= j; i++)
			x += y[i] * i * i;
		return x;
	}

	/**
	 * The partial sum D from C. A. Glasbey, "An analysis of histogram-based
	 * thresholding algorithms," CVGIP: Graphical Models and Image Processing,
	 * vol. 55, pp. 532-537, 1993.
	 */
	public static double D(long[] y, int j) {
		double x = 0;
		for (var i = 0; i <= j; i++)
			x += y[i] * i * i * i;
		return x;
	}
}
