res.setContentType("image/gif");
ServletOutputStream out = res.getOutputStream();
// Get the image location from the path info
URL source = ServletUtils.getResource(getServletContext(),
req.getPathInfo());
if (source == null) {
res.sendError(res.SC_NOT_FOUND,
"Extra path information must point to an image");
return;
}
// Construct an unshown frame
// No addNotify() because 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) {
res.sendError(res.SC_INTERNAL_SERVER_ERROR,
"Interrupted while loading image: " +
ServletUtils.getStackTraceAsString(e));
return;
}
// Get the size of the image
int width = image.getWidth(frame);
int height = image.getHeight(frame);
// Make sure we are reading valid image data
if (width <= 0 || height <= 0) {
res.sendError(res.SC_NOT_FOUND,
"Extra path information must point to a valid image");
return;
}
// Create an image to match, run through a filter
Image filtered = frame.createImage(
new FilteredImageSource(image.getSource(),
new GrayscaleImageFilter()));
// Encode and return the filtered image
GifEncoder encoder = new GifEncoder(filtered, out);
encoder.encode();
