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/*
 * #%L
 * Image processing operations for SciJava Ops.
 * %%
 * Copyright (C) 2014 - 2024 SciJava developers.
 * %%
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 * modification, are permitted provided that the following conditions are met:
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 *    this list of conditions and the following disclaimer.
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package org.scijava.ops.image.features.zernike;

/**
 * class used to represent a zernike moment polynomial.
 *
 * @author Andreas Graumann (University of Konstanz)
 */
public class Polynom {

	/** the array of polynom coefficients. */
	private final int[] m_coefficients;

	/** the degree of the polynom. */
	private final int m_degree;

	/**
	 * default constructor.
	 *
	 * @param degree the degree of the polynom
	 */
	public Polynom(final int degree) {
		m_degree = degree;
		m_coefficients = new int[m_degree + 1];
		for (int i = 0; i <= m_degree; ++i) {
			setCoefficient(i, 0);
		}
	}

	/**
	 * set the coefficient at a position.
	 *
	 * @param pos the position (the power of the monom)
	 * @param coef the coefficient
	 */
	public void setCoefficient(final int pos, final int coef) {
		m_coefficients[pos] = coef;
	}

	/**
	 * return the coefficient at a given position.
	 *
	 * @param pos the position
	 * @return the coefficient
	 */
	public int getCoefficient(final int pos) {
		return m_coefficients[pos];
	}

	/**
	 * return the value of the polynom in a given point.
	 *
	 * @param x the point
	 * @return the value of the polynom
	 */
	public double evaluate(final double x) {
		double power = 1.0;
		double result = 0.0;
		for (int i = 0; i <= m_degree; ++i) {
			result += m_coefficients[i] * power;
			power *= x;
		}
		return result;
	}

	/**
	 * provide a String representation of this polynom. mostly for debugging
	 * purposes and for the JUnit test case
	 *
	 * @return the String representation
	 */
	@Override
	public String toString() {
		final StringBuffer result = new StringBuffer();
		for (int i = m_degree; i >= 0; i--) {
			if (m_coefficients[i] != 0) {
				result.append(m_coefficients[i] + "X^" + i + " ");
			}
		}
		return result.toString();
	}
}