ServletOutputStream out = res.getOutputStream();
Graphics g = null;
try {
// Get the image location from the path info
// Use ServletUtils (Chapter 4) for safety
URL source =
ServletUtils.getResource(getServletContext(), req.getPathInfo());
// Load the image (from bytes to an Image object)
MediaTracker mt = new MediaTracker(frame); // frame acts as ImageObserver
Image image = Toolkit.getDefaultToolkit().getImage(source);
mt.addImage(image, 0);
try {
mt.waitForAll();
}
catch (InterruptedException e) {
res.sendError(res.SC_INTERNAL_SERVER_ERROR,
"Interrupted while loading image: " +
ServletUtils.getStackTraceAsString(e));
return;
}
// Get the width and height
int w = image.getWidth(frame);
int h = image.getHeight(frame);
// Make sure we are reading valid image data
if (w <= 0 || h <= 0) {
res.sendError(res.SC_NOT_FOUND,
"Extra path information must point to a valid image");
return;
}
// Construct a matching-size off screen graphics context
Image offscreen = frame.createImage(w, h);
g = offscreen.getGraphics();
// Draw the image to the off-screen graphics context
g.drawImage(image, 0, 0, frame);
// Write CONFIDENTIAL over its top
g.setFont(new Font("Monospaced", Font.BOLD | Font.ITALIC, 30));
g.drawString("CONFIDENTIAL", 10, 30);
// Encode the off-screen graphics into a GIF and send it to the client
res.setContentType("image/gif");
GifEncoder encoder = new GifEncoder(offscreen, out);
encoder.encode();
}
finally {
// Clean up resources
if (g != null) g.dispose();
}
