Reading an image from input stream

Question

Hello all,
I'm familiar with setting up an input stream but I have never actually done it. I'm making a connection to a URL (a JPG image). I would like to read the JPG from the URL using an input stream. With the URL class I was able to open a stream, however, I'm not exactly sure how to read from it.
I'm aware of the read() method and read(byte[]) methods of inputstream. But how do I actually implement it?
If I use read(), then bytes come in individually... do I need to combine them at one point? If I read the bytes into an array, how do I determine what size to set the array and how do I convert the byte array into an Image or ImageIcon?
Please advise.
R. Alcazar

Answer 1

Hi,
See http://java.sun.com/products/jdk/1.2/docs/guide/2d/api-jpeg/
and especially JPEGCodec.createJPEGDecoder(java.io.InputStream).
Anyway, you might not want to do it with InputStream. Instead you could try something like this:
URLConnection con = // get it somehow
Image i = (Image) con.getContent(new Class[] {Image.class});
However, If you still want to use the InputStream, here you go with some pseudo code:
InputStream in = // get the input stream with JPEG data...
JPEGImageDecoder dec = JPEGCodec.createJPEGDecoder(in);
Image i = dec.decodeAsBufferedImage();
You can get the InputStream from the URLConnection with getInputStream(). However, I don't remember if the InputStream contained also the HTTP (or what ever protocol the URL specifies) headers. If it contains the headers, then you must rip them of before giving the InputStream to the JPEGCodec...
If this is the case, try calling the URLConnection.getHeaderFields() method before getInputStream. This might not work though.