source: osm/utils/josm/plugins/landsat/src/landsat/WMSImage.java@ 1567

package landsat;

import java.awt.Graphics;
import java.awt.Image;
import java.awt.Point;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.coor.EastNorth;
import org.openstreetmap.josm.data.coor.LatLon;
import org.openstreetmap.josm.gui.NavigatableComponent;

public class WMSImage
{
        String constURL;
        protected Image theImage;
        protected double grabbedScale;
        protected EastNorth topLeft, bottomRight;
        double dEast, dNorth;   

        public WMSImage(String constURL)
        {
                this.constURL = constURL;
        }

        public void grab(NavigatableComponent nc) throws IOException
        {

                EastNorth topLeft  = nc.getEastNorth(0,0);
                grabbedScale =  nc.getScale();  // scale is enPerPixel

                this.topLeft = topLeft;

                try
                {
                        URL url = getURL(nc);
                        doGrab(url);
                }
                catch(MalformedURLException e)
                {
                        System.out.println("Illegal url. Error="+e);
                }
        }

        public void grab(NavigatableComponent nc,double minlat,double minlon,
                        double maxlat,double maxlon) throws IOException
        {
                LatLon p = new LatLon(minlat,minlon),
                                p2 = new LatLon(maxlat,maxlon);

                grabbedScale = nc.getScale(); // enPerPixel

                topLeft = Main.proj.latlon2eastNorth(new LatLon(maxlat,minlon));
                bottomRight = Main.proj.latlon2eastNorth(new LatLon(minlat,maxlon));

                int widthPx = (int)((bottomRight.east()-topLeft.east())/grabbedScale),
                heightPx = (int)
                ((topLeft.north()-bottomRight.north()) / grabbedScale);

                try
                {
                        URL url =  doGetURL(p.lon(),p.lat(),
                                                                        p2.lon(),p2.lat(),widthPx,heightPx);
                        doGrab(url);
                }
                catch(MalformedURLException e)
                {
                        System.out.println("Illegal url. Error="+e);
                }
        }

        private URL getURL(NavigatableComponent nc) throws MalformedURLException
        {
                double widthEN = nc.getWidth()*grabbedScale,
                heightEN = nc.getHeight()*grabbedScale;
                LatLon p = Main.proj.eastNorth2latlon(new EastNorth
                                (topLeft.east(), topLeft.north()-heightEN));
                LatLon p2 = Main.proj.eastNorth2latlon(new EastNorth
                                (topLeft.east()+widthEN, topLeft.north()));
                return doGetURL(p.lon(),p.lat(),p2.lon(),p2.lat(),
                                                (int)(widthEN/grabbedScale),
                                                (int)(heightEN/grabbedScale) );
        }

        protected URL doGetURL(double w,double s,double e,double n, int wi, 
                                        int ht) throws MalformedURLException
        {
                String str = constURL + "&bbox=" + w +"," + s + ","+
                                e+","+n + "&width=" + wi + "&height=" + ht;
                return new URL(str);
        }

        protected void doGrab (URL url) throws IOException
        {
                InputStream is = url.openStream();
                theImage = ImageIO.read(is) ;
                is.close();
                Main.map.repaint();
        }

        public void displace (double dEast, double dNorth)
        {
                this.dEast += dEast;    
                this.dNorth += dNorth;  
        }

        public boolean contains(EastNorth eastNorth)
        {
                double e1 = topLeft.east()+dEast, 
                           e2 = bottomRight.east()+dEast,
                           n1 = bottomRight.north()+dNorth,
                           n2 = topLeft.north()+dNorth;

                boolean b =  eastNorth.east()>=e1 && eastNorth.east()<=e2 &&
                                eastNorth.north()>=n1 && eastNorth.north()<=n2;
                return b;
        }

        public void paint(Graphics g,NavigatableComponent nc) 
        {
                if(theImage!=null)
                {
                        double zoomInFactor = grabbedScale / nc.getScale();

                        // Find the image x and y of the supplied bottom left
                        // This will be the difference in EastNorth units, divided by the
                        // grabbed scale in EastNorth/pixel.

                        int w = theImage.getWidth(null), h=theImage.getHeight(null);
                        EastNorth topLeftDisplaced  = 
                                new EastNorth(topLeft.east()+dEast, topLeft.north()+dNorth);
                        Point displacement = Main.map.mapView.getPoint(topLeftDisplaced);
                        g.drawImage(theImage,displacement.x,displacement.y,
                                        (int)(displacement.x+w*zoomInFactor),
                                        (int)(displacement.y+h*zoomInFactor),
                                        0,0,w,h,null);
                }
        }

}