/*=========================================================================

  Program:   FusionViewer
  Module:    $RCSfile: WindowLevelModel.java,v $
  Language:  Java
  Date:      $Date: 2007/02/02 19:27:11 $
  Version:   $Revision: 1.2 $
  
  Copyright (c) Insightful Corporation.  All rights reserved.
  See Copyright.txt for details.
  
  This software is distributed WITHOUT ANY WARRANTY; without even
  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
  PURPOSE.  See the above copyright notice for more information.

=========================================================================*/

package org.fusionviewer.model;

import org.fusionviewer.display.Image;


/**\class WindowLevelModel
 *\brief Pixel value scaling parameters
 * 
 * 		outputPixelValue = slope * inputPixelValue + offset
 * 
 * In terms of window and level
 * 
 * 		slope = MAX_PIXEL_VALUE / window
 * 		offset = level - window / 2
 */
public class WindowLevelModel {
	/*
	 * These members are described above
	 */
	private float offset, slope, window, level;
	private float minValue, pixelRange;
	
	
	/**
	 * Initialize window and level parameters from an image so that all
	 * values are linearly scaled to fill an 8-bit display range
	 * 
	 * @param image an image
	 */
	public void initialize(Image image) {
		if (image == null)
			return;
		
		float maxValue = (float) image.getMaxValue();
		minValue = (float) image.getMinValue();
		
		if (image.isByteType()) {
			slope = 1.0f;
			offset = 0.0f;
			
			window = 255.0f;
			level = 255.0f / 2.0f;
			
			minValue = 0.0f;
			pixelRange = 255.0f;
		} else if (maxValue == minValue) {
			// Trap here to avoid a slope of zero
			slope = 1.0f;
			offset = minValue;
			
			window = 1.0f;
			level = minValue;
			
			minValue = 0.0f;
			pixelRange = 1.0f;
		} else {
			pixelRange = maxValue - minValue;
			slope = 255.0f / (float)(pixelRange);
			offset = minValue;
			
			window = pixelRange;
			level = pixelRange / 2.0f + minValue;
			}
	}
	
	/**
	 * Get the pixel scaling offset: output = slope * input + offset
	 * 
	 * @return scaling offset
	 */
	public float getOffset() {
		return offset;
	}
	
	/**
	 * Get the pixel scaling slope: output = slope * input + offset
	 * 
	 * @return scaling slope
	 */
	public float getSlope() {
		return slope;
	}
	
	/**
	 * Get the pixel scaling window
	 * 
	 * @return scaling window
	 */
	public float getWindow() {
		return window;
	}
	
	/**
	 * Get the pixel scaling level
	 * 
	 * @return scaling level
	 */
	public float getLevel() {
		return level;
	}
	
	/**
	 * @return the minimum value of the image this model was initialized from
	 */
	public float getMinValue() {
		return minValue;
	}
	
	/**
	 * @return the range of pixel values in the image this model was initialized from
	 */
	public float getPixelRange() {
		return pixelRange;
	}
	
	/**
	 * Set the pixel scaling: output = slope * input + offset
	 * 
	 * @param offset scaling offset
	 * @param slope scaling slope
	 * @return true if this object was modified
	 */
	public boolean setOffsetSlope(float offset, float slope) {
		if ((slope == this.slope) && (offset == this.offset))
			return false;
		
		this.offset = offset;
		this.slope = slope;
		this.window = this.slope * 255.0f;
		this.level = offset + this.window / 2.0f;
				
		return true;
	}
	
	/**
	 * Set the pixel scaling as window and level.
	 * 		output = MAX_PIXEL_VALUE / window * input + (level - window / 2)
	 * 
	 * @param window scaling window
	 * @param level scaling level
	 * @return true if this object was modified
	 */
	public boolean setWindowLevel(float window, float level) {
		if ((window == this.window) && (level == this.level))
			return false;
		
		this.window = window;
		this.level = level;
		
		this.offset = level - (window / 2.0f);
		this.slope = 255.0f / window;
		
		return true;
	}
}