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ImageJ is an open source Java image processing program inspired by NIH Image for the Macintosh.
There is a newer version: 1.54m
package ij.process;
import java.awt.Rectangle;
import java.awt.Polygon;
import java.awt.geom.Rectangle2D;

/** Used by the Roi classes to return float coordinate arrays and to
	determine if a point is inside or outside of spline fitted selections. */
public class FloatPolygon {
	private Rectangle bounds;
	private float minX, minY, maxX, maxY;

	/** The number of points. */
	public int npoints;

	/* The array of x coordinates. */
	public float xpoints[];

	/* The array of y coordinates. */
	public float ypoints[];

	/** Constructs an empty FloatPolygon. */ 
	public FloatPolygon() {
		npoints = 0;
		xpoints = new float[10];
		ypoints = new float[10];
	}

	/** Constructs a FloatPolygon from x and y arrays. */ 
	public FloatPolygon(float xpoints[], float ypoints[]) {
		if (xpoints.length!=ypoints.length)
			throw new IllegalArgumentException("xpoints.length!=ypoints.length");
		this.npoints = xpoints.length;
		this.xpoints = xpoints;
		this.ypoints = ypoints;
	}

	/** Constructs a FloatPolygon from x and y arrays. */ 
	public FloatPolygon(float xpoints[], float ypoints[], int npoints) {
		this.npoints = npoints;
		this.xpoints = xpoints;
		this.ypoints = ypoints;
	}
		
	/** Returns 'true' if the point (x,y) is inside this polygon. This is a Java
	 *  version of the remarkably small C program by W. Randolph Franklin at
	 *  http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html#The%20C%20Code
	 * 
	 *  In the absence of numerical errors, x coordinates exactly at a boundary are taken as if
	 *  in the area immediately at the left of the boundary. For horizontal boundaries,
	 *  y coordinates exactly at the border are taken as if in the area immediately above it
	 *  (i.e., in decreasing y direction).
	 *  The ImageJ convention of an offset of 0.5 pixels between pixel centers and outline
	 *  coordinates is not taken into consideration; this method returns the purely
	 *  geometrical relationship.
	 */
	public boolean contains(double x, double y) {
		boolean inside = false;
		for (int i=0, j=npoints-1; i=y)!=(ypoints[j]>=y)) &&
					(x>((double)xpoints[j]-xpoints[i])*((double)y-ypoints[i])/((double)ypoints[j]-ypoints[i])+(double)xpoints[i]))
				inside = !inside;
		}
		return inside;
	}

	/** A version of contains() that accepts float arguments. */
	public boolean contains(float x, float y) {
		return contains((double)x, (double)y);
	}

	public Rectangle getBounds() {
		if (npoints==0)
			return new Rectangle();
		if (bounds==null)
			calculateBounds(xpoints, ypoints, npoints);
		return bounds.getBounds();
	}

	public Rectangle2D.Double getFloatBounds() {
		if (npoints==0)
			return new Rectangle2D.Double();
		if (bounds==null)
			calculateBounds(xpoints, ypoints, npoints);
		return new Rectangle2D.Double(minX, minY, maxX-minX, maxY-minY);
	}

	void calculateBounds(float[] xpoints, float[] ypoints, int npoints) {
		minX = Float.MAX_VALUE;
		minY = Float.MAX_VALUE;
		maxX = Float.MIN_VALUE;
		maxY = Float.MIN_VALUE;
		for (int i=0; i d2sqr;
				}
				if (determinate > 0 || collinearAndFurther) {
					x2=x3; y2=y3; p2=p3;       // p2 is not on the convex hull, p3 becomes the new candidate
				}
				p3 ++; if (p3==npoints) p3 = 0;
			} while (p3 != p1);                // all points have been checked whether they are the next one on the convex hull

			xx[n2] = (float)x1;                // save p1 as a point on the convex hull
			yy[n2] = (float)y1;
			n2++;

			if (p2 == p1) break;               // happens only if there was only one unique point
			p1 = p2;
			if (n2 > 1 && xpoints[p1]==xx[0] && ypoints[p1]==yy[0]) break; //all done but pstart was missed because of duplicate points
		} while (p1!=pstart);
		return new FloatPolygon(xx, yy, n2);
	}
	
	public synchronized void translate(double x, double y) {
		float fx = (float)x;
		float fy = (float)y;
		for (int i=0; i