ServletOutputStream out = res.getOutputStream();
String contentType = req.getContentType();
if (contentType == null || !contentType.startsWith("image")) {
throw new ServletException("Incoming content type must be \"image/*\"");
}
// Fetch the bytes of the incoming image
DataInputStream in = new DataInputStream(
new BufferedInputStream(
req.getInputStream()));
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[4 * 1024]; // 4K buffer
int len;
while ((len = in.read(buf, 0, buf.length)) != -1) {
baos.write(buf, 0, len);
}
// Create an image out of them
Image image = Toolkit.getDefaultToolkit()
.createImage(baos.toByteArray());
// Construct an unshown frame
// No addNotify() since it's peer isn't needed
Frame frame = new Frame();
// Load the image, so we can get a true width and height
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());
}
// Shrink the image to half its width and half its height.
// An improved version of this servlet would receive the desired
// ratios in its init parameters.
// We could also resize using ReplicateScaleFilter or
// AreaAveragingScaleFilter.
Image shrunk = image.getScaledInstance(image.getWidth(frame) / 2,
image.getHeight(frame) / 2,
image.SCALE_DEFAULT);
// Encode and return the shrunken image
res.setContentType("image/gif");
GifEncoder encoder = new GifEncoder(shrunk, out);
encoder.encode();
