res.setContentType("image/gif");
ServletOutputStream out = res.getOutputStream();
// Get the image location from the path info
String source = req.getPathTranslated();
if (source == null) {
throw new ServletException("Extra path information " +
"must point to an image");
}
// Short circuit if it's been done before
if (gifs.containsKey(source)) {
ByteArrayOutputStream baos = (ByteArrayOutputStream) gifs.get(source);
baos.writeTo(out);
return;
}
// Construct an unshown frame
// No addNotify() since its peer isn't needed
Frame frame = new Frame();
// Load the image
Image image = Toolkit.getDefaultToolkit().getImage(source);
MediaTracker mt = new MediaTracker(frame);
mt.addImage(image, 0);
try {
mt.waitForAll();
}
catch (InterruptedException e) {
getServletContext().log(e, "Interrupted while loading image");
throw new ServletException(e.getMessage());
}
// Get the size of the image
int width = image.getWidth(frame);
int height = image.getHeight(frame);
// Create an image to match, run through a filter
Image filtered = frame.createImage(
new FilteredImageSource(image.getSource(),
new GrayscaleImageFilter()));
// Encode, store, and return the filtered image
ByteArrayOutputStream baos = new ByteArrayOutputStream();
GifEncoder encoder = new GifEncoder(filtered, baos);
encoder.encode();
gifs.put(source, baos);
baos.writeTo(out);
