// BlackColorCoder.java
//
// 
// Copyright 2004, Ethan Bolker and Bogdan Calota

package edu.umb.cs.eb.folding;

import java.awt.Color;

/**
 *  Interpolate between colors in HSB model.
 */
public class BlackColorCoder
{
    private float k = (float)0.5;

    // It's easy to solve for a, b and c in terms of k:

    private float a;
    private float b;
    private float c;

    public BlackColorCoder() 
    {
	this( (float)0.5 );
    }

    public BlackColorCoder( float k )
    {
	this.k = k;
	a =  4 - 4*k;
	b = -6 + 6*k;
	c =  3 - 2*k;
    }

    protected Color getCellColor( double hydrophobicIndex ) 
    {
	return getCellColor( (float)hydrophobicIndex );
    }

    protected Color getCellColor( float hydrophobicIndex ) 
    {
	// maps hydrophobic index from [-1, 1] into [0, 1]
	float x = (hydrophobicIndex + 1)/2;
	
	// transforms linear into cubic interpolation
	float alpha = x * ( c + x * ( b + a * x ));
	//float alpha = x;

	// transform the mapping so that [0,1] goes into [1,0]
	//   so that red( now black) is 1 and green( now white) is -1,
	//   where 1 and -1 represent the hydrophobic indices
	float colorIndex = 1.0f - alpha;

	// map the index between 0 and 150 to obtain the color shade
	//   map into [0, 150] and then into [100,250]
	float shade = 100 + colorIndex * 150;  
	
	// create and return color
	return new Color( (int) shade, (int) shade, (int) shade);


    }

}