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Core visualization support for the JUNG project
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/*
 * Copyright (c) 2005, The JUNG Authors
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either "license.txt"
 * or https://github.com/jrtom/jung/blob/master/LICENSE for a description.
 *
 * Created on Jun 17, 2005
 */

package edu.uci.ics.jung.visualization;

import java.awt.Shape;
import java.awt.geom.Area;
import java.awt.geom.GeneralPath;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.awt.image.BufferedImage;

/**
 * Provides Supplier methods that, given a BufferedImage, an Image,
 * or the fileName of an image, will return a java.awt.Shape that
 * is the contiguous traced outline of the opaque part of the image.
 * This could be used to define an image for use in a Vertex, where
 * the shape used for picking and edge-arrow placement follows the
 * opaque part of an image that has a transparent background.
 * The methods try to detect lines in order to minimize points
 * in the path
 * 
 * @author Tom Nelson
 *
 * 
 */
public class FourPassImageShaper {
    
    public static Shape getShape(BufferedImage image) {
        Area area = new Area(leftEdge(image));
        area.intersect(new Area(bottomEdge(image)));
        area.intersect(new Area(rightEdge(image)));
        area.intersect(new Area(topEdge(image)));
        return area;
    }
    /**
     * Checks to see if point p is on a line that passes thru
     * points p1 and p2. If p is on the line, extend the line
     * segment so that it is from p1 to the location of p.
     * If the point p is not on the line, update my shape
     * with a line extending to the old p2 location, make
     * the old p2 the new p1, and make p2 the old p
     * @param p1
     * @param p2
     * @param p
     * @param line
     * @param path
     * @return
     */
    private static Point2D detectLine(Point2D p1, Point2D p2, Point2D p, 
            Line2D line, GeneralPath path) {
    	
        // check for line
        // if p is on the line that extends thru p1 and p2
    	if(line.ptLineDistSq(p) == 0) { // p is on the line p1,p2
            // extend line so that p2 is at p
            p2.setLocation(p);
        } else { // its not on the current line
        	// start a new line from p2 to p
            p1.setLocation(p2);
            p2.setLocation(p);
            line.setLine(p1,p2);
            // end the ongoing path line at the new p1 (the old p2)
            path.lineTo((float)p1.getX(), (float)p1.getY());
        }
        return p2;
    }
    /**
     * trace the left side of the image
     * @param image
     * @param path
     * @return
     */
    private static Shape leftEdge(BufferedImage image) {
        GeneralPath path = new GeneralPath();
        Point2D p1 = null;
        Point2D p2 = null;
        Line2D line = new Line2D.Float();
        Point2D p = new Point2D.Float();
        int foundPointY = -1;
        for(int i=0; i= 0) {
            	if(p2 == null) {
            		// this is the first point found. project line to right edge
            		p1 = new Point2D.Float(image.getWidth()-1, foundPointY);
            		path.moveTo(p1.getX(), p1.getY());
            		p2 = new Point2D.Float();
            		p2.setLocation(p);
            	} else {
            		p2 = detectLine(p1, p2, p, line, path);
            	}
            }
        }
        path.lineTo(p.getX(), p.getY());
        if(foundPointY >= 0) {
        	path.lineTo(image.getWidth()-1, foundPointY);
        }
        path.closePath();
        return path;
    }
    
    /**
     * trace the bottom of the image
     * @param image
     * @param path
     * @param start
     * @return
     */
    private static Shape bottomEdge(BufferedImage image) {
        GeneralPath path = new GeneralPath();
        Point2D p1 = null;
        Point2D p2 = null;
        Line2D line = new Line2D.Float();
        Point2D p = new Point2D.Float();
        int foundPointX = -1;
        for(int i=0; i=0; j--) {
                if((image.getRGB(i,j) & 0xff000000) != 0) {
                    // this is a point I want
                    p.setLocation(i,j);
                    foundPointX = i;
                    break;
                }
            }
            if(foundPointX >= 0) {
            	if(p2 == null) {
            		// this is the first point found. project line to top edge
            		p1 = new Point2D.Float(foundPointX, 0);
            		// path starts here
            		path.moveTo(p1.getX(), p1.getY());
            		p2 = new Point2D.Float();
            		p2.setLocation(p);
            	} else {
            		p2 = detectLine(p1, p2, p, line, path);
            	}
            }
        }
        path.lineTo(p.getX(), p.getY());
        if(foundPointX >= 0) {
        	path.lineTo(foundPointX, 0);
        }
        path.closePath();
        return path;
    }
    
    /**
     * trace the right side of the image
     * @param image
     * @param path
     * @param start
     * @return
     */
    private static Shape rightEdge(BufferedImage image) {
        GeneralPath path = new GeneralPath();
        Point2D p1 = null;
        Point2D p2 = null;
        Line2D line = new Line2D.Float();
        Point2D p = new Point2D.Float();
        int foundPointY = -1;
        
        for(int i=image.getHeight()-1; i>=0; i--) {
            for(int j=image.getWidth()-1; j>=0; j--) {
                if((image.getRGB(j,i) & 0xff000000) != 0) {
                    // this is a point I want
                    p.setLocation(j,i);
                    foundPointY = i;
                    break;
                }
            }
            if(foundPointY >= 0) {
            	if(p2 == null) {
            		// this is the first point found. project line to top edge
            		p1 = new Point2D.Float(0, foundPointY);
            		// path starts here
            		path.moveTo(p1.getX(), p1.getY());
            		p2 = new Point2D.Float();
            		p2.setLocation(p);
            	} else {
            		p2 = detectLine(p1, p2, p, line, path);
            	}
            }
        }
        path.lineTo(p.getX(), p.getY());
        if(foundPointY >= 0) {
        	path.lineTo(0, foundPointY);
        }
        path.closePath();
        return path;
    }
    
    /**
     * trace the top of the image
     * @param image
     * @param path
     * @param start
     * @return
     */
    private static Shape topEdge(BufferedImage image) {
        GeneralPath path = new GeneralPath();
        Point2D p1 = null;
        Point2D p2 = null;
        Line2D line = new Line2D.Float();
        Point2D p = new Point2D.Float();
        int foundPointX = -1;
        
        for(int i=image.getWidth()-1; i>=0; i--) {
            for(int j=0; j= 0) {
            	if(p2 == null) {
            		// this is the first point found. project line to top edge
            		p1 = new Point2D.Float(foundPointX, image.getHeight()-1);
            		// path starts here
            		path.moveTo(p1.getX(), p1.getY());
            		p2 = new Point2D.Float();
            		p2.setLocation(p);
            	} else {
            		p2 = detectLine(p1, p2, p, line, path);
            	}
            }
        }
        path.lineTo(p.getX(), p.getY());
        if(foundPointX >= 0) {
        	path.lineTo(foundPointX, image.getHeight()-1);
        }
        path.closePath();
        return path;
    }
}