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 * Image processing operations for SciJava Ops.
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package org.scijava.ops.image.threshold.mean;

import org.scijava.ops.image.threshold.AbstractComputeThresholdHistogram;
import net.imglib2.histogram.Histogram1d;
import net.imglib2.type.numeric.RealType;

// NB - this plugin adapted from Gabriel Landini's code of his AutoThreshold
// plugin found in Fiji (version 1.14).

/**
 * Implements a mean threshold method by Glasbey.
 *
 * @author Barry DeZonia
 * @author Gabriel Landini
 * @implNote op names='threshold.mean'
 */
public class ComputeMeanThreshold<T extends RealType<T>> extends
	AbstractComputeThresholdHistogram<T>
{

	/**
	 * TODO
	 *
	 * @param hist the {@link Histogram1d}
	 * @return the Mean threshold value
	 */
	@Override
	public long computeBin(final Histogram1d<T> hist) {
		final var histogram = hist.toLongArray();
		return computeBin(histogram);
	}

	/**
	 * C. A. Glasbey,<br>
	 * "An analysis of histogram-based thresholding algorithms,"<br>
	 * CVGIP: Graphical Models and Image Processing, vol. 55, pp. 532-537,<br>
	 * 1993.
	 * <P>
	 * The threshold is the mean of the greyscale data
	 */
	public static long computeBin(final long[] histogram) {
        var threshold = -1;
		double tot = 0, sum = 0;
		for (var i = 0; i < histogram.length; i++) {
			tot += histogram[i];
			sum += (i * histogram[i]);
		}
		threshold = (int) Math.floor(sum / tot);
		return threshold;
	}

}
