jpeghelper.java

openmap java写的开源数字地图程序. 用applet实现,可以像google map 那样放大缩小地图.

// **********************************************************************
// 
// <copyright>
// 
//  BBN Technologies
//  10 Moulton Street
//  Cambridge, MA 02138
//  [phone]
// 
//  Copyright (C) BBNT Solutions LLC. All rights reserved.
// 
// </copyright>
// **********************************************************************
// 
// $Source: /cvs/distapps/openmap/src/openmap/com/bbn/openmap/image/JPEGHelper.java,v $
// $RCSfile: JPEGHelper.java,v $
// $Revision: 1.2.2.1 $
// $Date: 2004/10/14 18:26:59 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.image;

import com.sun.image.codec.jpeg.*;
import java.io.*;
import java.awt.image.*;
import java.net.URL;

import com.bbn.openmap.util.Debug;

/**
 * This class provides some utility methods for creating jpeg encoded
 * images. It relies on the Sun JDK/SDK JPEG codec classes.
 */
public class JPEGHelper {

    /**
     * This class has only static methods, so there is no need to
     * construct anything.
     */
    private JPEGHelper() {};

    /**
     * Return a byte array that contains the JPEG encoded image.
     * 
     * @param image the image to encode
     * @param quality the JPEG quality factor to use in encoding
     * @exception IOException an error occured in encoding the image
     */
    public static byte[] encodeJPEG(BufferedImage image, float quality)
            throws IOException {

        ByteArrayOutputStream out = new ByteArrayOutputStream();
        if (Debug.debugging("jpeghelper")) {
            Debug.output("Got output stream..." + out);
        }

        JPEGEncodeParam param = JPEGCodec.getDefaultJPEGEncodeParam(image);
        param.setQuality(quality, true);
        if (Debug.debugging("jpeghelper")) {
            Debug.output("Got encode params...");
        }

        JPEGImageEncoder enc = JPEGCodec.createJPEGEncoder(out, param);
        if (Debug.debugging("jpeghelper")) {
            Debug.output("Got jpeg encoder...");
        }

        enc.encode(image);
        if (Debug.debugging("jpeghelper")) {
            Debug.output("encoded?");
        }

        return out.toByteArray();
    }

    /**
     * Return a byte array that contains the JPEG encoded image.
     * 
     * @param w the width of the image
     * @param h the height of the image
     * @param pixels the array of pixels in RGB directcolor
     * @param quality the JPEG quality factor to use in encoding
     * @exception IOException an error occured in encoding the image
     */
    public static byte[] encodeJPEG(int w, int h, int[] pixels, float quality)
            throws IOException {
        BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        bi.setRGB(0, 0, w, h, pixels, 0, w);
        pixels = null;
        return encodeJPEG(bi, quality);
    }

    /**
     * A test main that encodes an image url at various jpeg quality
     * factors.
     * 
     * @param args url [width height]
     */
    public static void main(String args[]) throws Exception {
        if (args.length == 0) {
            System.out.println("java jpeg url [width height]");
            System.exit(-1);
        }

        Debug.init();

        int uw = -1;
        int uh = -1;
        if (args.length > 1) {
            uw = Integer.parseInt(args[1]);
            uh = Integer.parseInt(args[2]);
        }

        String urlsource = args[0];
        int lastslash = urlsource.lastIndexOf('/');
        if (lastslash == -1) {
            lastslash = 0;
        } else {
            lastslash++;
        }
        int lastdot = urlsource.lastIndexOf('.');
        if (lastdot == -1) {
            lastdot = 0;
        }
        String filebase = urlsource.substring(lastslash, lastdot);

        Debug.output("url=" + urlsource + " filebase=" + filebase);

        BufferedImage bi = BufferedImageHelper.getBufferedImage(new URL(urlsource),
                0,
                0,
                uw,
                uh);
        if (bi == null) {
            Debug.error("JPEGHelper: Image load failed");
        } else {
            PrintStream html = new PrintStream(new FileOutputStream(new File(filebase
                    + ".html")));

            html.println("Source url = " + urlsource + " <br>");
            html.println(" width = " + uw + " height=" + uh + " pixels=" + uw
                    * uh + " <hr>");
            for (int i = 0; i < 20; i++) {
                File f = new File(filebase + ((i < 10) ? "0" : "") + i + ".jpg");
                float quality = 0.0499f * i;
                byte data[] = encodeJPEG(bi, quality);
                OutputStream writef = new FileOutputStream(f);
                writef.write(data);
                writef.close();
                html.println("Image Quality Factor: " + quality + " <br>");
                html.println("Image Size (bytes) : " + data.length + " <br>");
                html.println("<img src=\"" + f.getName() + "\"> <hr>");
            }

            html.close();
        }
        System.exit(-1); //awt stinks
    }
}