content: // ===============================================================================
  // Authors: AFRL/RQQD
  // Organization: Air Force Research Laboratory, Aerospace Systems Directorate, Power and Control Division
  // 
  // Copyright (c) 2017 Government of the United State of America, as represented by
  // the Secretary of the Air Force.  No copyright is claimed in the United States under
  // Title 17, U.S. Code.  All Other Rights Reserved.
  // ===============================================================================
  
  /*
   * GRAL: GRAphing Library for Java(R)
   *
   * (C) Copyright 2009-2013 Erich Seifert <dev[at]erichseifert.de>,
   * Michael Seifert <mseifert[at]error-reports.org>
   *
   * This file is part of GRAL.
   *
   * GRAL is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Lesser General Public License as published by
   * the Free Software Foundation, either version 3 of the License, or
   * (at your option) any later version.
   *
   * GRAL is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public License
   * along with GRAL.  If not, see <http://www.gnu.org/licenses/>.
   */
  package de.erichseifert.gral.plots.colors;
  
  import java.awt.Color;
  import java.awt.Paint;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  
  import de.erichseifert.gral.util.MathUtils;
  
  /**
   * Linearly blends different colors for values between 0.0 and 1.0.
   */
  public class LinearGradient extends ScaledContinuousColorMapper {
  	/** Version id for serialization. */
  	private static final long serialVersionUID = 4256873420364549677L;
  
  	/** Colors that will be used for blending. **/
  	private final List<Color> colors;
  
  	/**
  	 * Creates a new instance with at least one color.
  	 * @param color1 First color.
  	 * @param colors Additional colors.
  	 */
  	public LinearGradient(Color color1, Color... colors) {
  		this.colors = new ArrayList<Color>();
  		this.colors.add(color1);
  		this.colors.addAll(Arrays.asList(colors));
  	}
  
  	/**
  	 * Returns the Paint according to the specified value.
  	 * @param value Value of color.
  	 * @return Paint.
  	 */
  	@Override
  	public Paint get(double value) {
  		Double v = scale(value);
  		v = applyMode(v, 0.0, 1.0);
  		if (!MathUtils.isCalculatable(v)) {
  			return null;
  		}
  
  		double x = v.doubleValue();
  		int colorMax = colors.size() - 1;
  		double pos = MathUtils.limit(x*colorMax, 0.0, colorMax);
  
  		if (pos == 0.0) {
  			return colors.get(0);
  		}
  		if (pos == colorMax) {
  			return colors.get(colorMax);
  		}
  
  		double fract = pos - (int) pos;
  		Color color1 = colors.get((int) pos);
  
  		if (fract == 0.0) {
  			return color1;
  		}
  
  		double fractInv = 1.0 - fract;
  		Color color2 = colors.get((int) pos + 1);
  
  		double r = fractInv*color1.getRed()   + fract*color2.getRed();
  		double g = fractInv*color1.getGreen() + fract*color2.getGreen();
  		double b = fractInv*color1.getBlue()  + fract*color2.getBlue();
  		double a = fractInv*color1.getAlpha() + fract*color2.getAlpha();
  
  		return new Color(
  			(int) Math.round(r),
  			(int) Math.round(g),
  			(int) Math.round(b),
  			(int) Math.round(a)
  		);
  	}
  
  	@Override
  	public void setMode(Mode mode) {
  		super.setMode(mode);
  	}
  
  	/**
  	 * Returns the colors that are used for blending.
  	 * @return A list of colors in the order they will be used for blending.
  	 */
  	public List<Color> getColors() {
  		return Collections.unmodifiableList(colors);
  	}
  }
  