import java.awt.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.imageio.stream.*;
import java.io.*;
import java.net.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

/*
 * This servlet provides the service of labeling an
 * image with a text string.  The caller of the 
 * servlet gets to specify the image (local file or
 * URL), the text string, text size, and the color.
 * This servlet has a large number of limitations,
 * the foremost being that it will only write JPEG
 * images (with minimal compression).
 * <p>
 * Note: on X-based systems like Linux or Solaris, 
 * this servlet probably won't work unless the host
 * is running an X server.
 * <p>
 * This servlet requires the JAI/IIO package to be
 * installed to perform JPG image output.
 * <p>
 * Example img src URL:<br>
 * http://www.myhost.com/servlet/ImageLabelServer?src=http://www.foobar.com/logo.jpg&text=Foobar+Logo&size=28&color=90f000ff
 * <br>
 * This sample will cause the servlet to got retrieve the image logo.jpg from
 * the www.foobar.com web site, and then overlay the text "Foobar Logo" in 
 * partially transparent purple 28-point text.
 *
 * @author Neal Ziring
 */ 

public class ImageLabelServlet extends HttpServlet
{
    public static final String PARM_IMAGE = "src";
    public static final String PARM_TEXT = "text";
    public static final String PARM_SIZE = "size";
    public static final String PARM_COLOR= "color";

    public static final String IMG_OUT_SUFFIX = "jpg";
    public static final String IMG_OUT_MIME = "image/jpeg";

    /* need these for doing AWT stuff */
    static Component ob = null;
    static Toolkit tk = null;

    /**
     * Initialize stuff we need for this servlet.
     */
    public void init(ServletConfig conf) {
        if (tk == null) tk = Toolkit.getDefaultToolkit();
        if (ob == null) { ob = new Frame(); ob.addNotify(); }
    }

    /**
     * Just call the doGet method to handles posts.
     */
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, java.io.IOException
    {
        doGet(req,resp);
    }

    /**
     * Process a request - we look for the parameters
     * listed above.  Our output consists of an image
     * in image/jpeg format, or a 404 message if we 
     * couldn't load the requested image.
     */
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, java.io.IOException
    {
        String src = req.getParameter(PARM_IMAGE);
        if (src == null || src.length() == 0) {
            resp.sendError(resp.SC_BAD_REQUEST, "No source image specified");
            return;
        }
        String text = req.getParameter(PARM_TEXT);
        if (text == null || text.length() == 0)
            text = (new Date()).toString();
        String size = req.getParameter(PARM_SIZE);
        int textSize = 14;
        try { textSize = Integer.parseInt(size); } 
        catch (Exception ie) { }
        String color = req.getParameter(PARM_COLOR);
        int textColor = 0x666666;
        try { 
            if (color.startsWith("#")) color = color.substring(1);
            textColor = (int)(Long.parseLong(color, 16) & 0x0ffffffff);
        } catch (Exception ie2) { }
        float cq = 0.01F;
        String qual = req.getParameter("q");
        if (qual != null && qual.length() > 0) {
            try { cq = (float)(Double.parseDouble(qual)); }
            catch (Exception ie) { }
        }
        Font f = new Font("Sans-serif", Font.BOLD, textSize);
        Image img = null;
        if (src.indexOf('/') >= 0 || src.indexOf(':') >= 0) { try {
            URL u = new URL(src);
            img = tk.createImage(u);
        } catch (Exception ie3) { } }
        else { try {
            img = tk.createImage(src);
        } catch (Exception ie4) { } }

        MediaTracker mt = new MediaTracker(ob);
        mt.addImage(img, 2);
        try { mt.waitForID(2); } catch (InterruptedException eix) { }
        if (mt.isErrorID(2)) img = null;
        if (img == null) {
            resp.sendError(resp.SC_NOT_FOUND, "Could not load source image");
        }
        int w, h;
        w = img.getWidth(ob);
        h = img.getHeight(ob);
        BufferedImage img2 = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        if (img2 == null) System.err.println("img2 is Null!");
        Graphics g = img2.getGraphics();
        if (g == null) System.err.println("Graphics is Null!");
        Color c = new Color(textColor, (((textColor >> 24) & 0xff) != 0));
        g.setColor(c);
        g.setFont(f);
        g.drawImage(img, 0, 0, ob);
        g.drawString(text, textSize/2, (textSize * 5)/4);
        img.flush(); img = null;
        Iterator writers = ImageIO.getImageWritersBySuffix(IMG_OUT_SUFFIX);
        if (!(writers.hasNext())) {
            resp.sendError(resp.SC_CONFLICT, "Cannot write JPEG image!");
            return;
        }
        if (!writeImageOut((ImageWriter)(writers.next()), img2, resp, cq)) {
            resp.sendError(resp.SC_CONFLICT, "Writing image failed");
            return;
        }
        img2.flush(); img2 = null;
        return;
    }

    /**
     * Write out the image to the servlet response stream.
     * This method always sends a mime type of IMG_OUT_MIME.
     */
    boolean writeImageOut(ImageWriter wr, BufferedImage img, 
                          HttpServletResponse resp, float cq)
    {
        boolean ret = false;
        resp.setContentType(IMG_OUT_MIME);
        try {
            OutputStream oos = resp.getOutputStream();
            ImageOutputStream ios = ImageIO.createImageOutputStream(oos);
            wr.setOutput(ios);
            ImageWriteParam parm = wr.getDefaultWriteParam();
            parm.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
            parm.setCompressionQuality(cq);
            cq = parm.getCompressionQuality();
            IIOImage ii = new IIOImage(img, null, null);
            wr.prepareWriteSequence(null);
            wr.writeToSequence(ii, parm);
            wr.endWriteSequence();
            ios.flush();
            wr.dispose();
            ios.close();
            ret = true;
        }
        catch ( Exception ioe) {
            System.err.println("Error in image writing: " + ioe);
            ioe.printStackTrace();
        }
        return ret;
    }
}