How to grab byte[] of an Image in java?

Question

I have a url of an Image. Now I want to get the byte[] of that image. How can I get that image in byte form.

Actually the image is a captcha image. I am using decaptcher.com to solve that captcha. To send that captcha image to the decaptcher.com through its API, the image should in in bytes array.

That's why I want to get the image at the url to be in bytes form.

Answer 1

You may want to read this for reading an image in. ImageIO.Read(url) will give you a Buffered Image Which you can then ask for information. I use the getRGB method on BufferedReader to read individual pixels.

Answer 2

EDIT

From this SO question I've got how to read an input stream into a byte array.

Here's the revised program.

import java.io.*;
import java.net.*;

public class ReadBytes {
    public static void main( String [] args ) throws IOException {

     URL url = new URL("http://sstatic.net/so/img/logo.png");

            // Read the image ...
     InputStream inputStream      = url.openStream();
     ByteArrayOutputStream output = new ByteArrayOutputStream();
     byte [] buffer               = new byte[ 1024 ];

        int n = 0;
        while (-1 != (n = inputStream.read(buffer))) {
           output.write(buffer, 0, n);
        }
     inputStream.close();

     // Here's the content of the image...
     byte [] data = output.toByteArray();

 // Write it to a file just to compare...
 OutputStream out = new FileOutputStream("data.png");
 out.write( data );
 out.close();

 // Print it to stdout 
     for( byte b : data ) {
      System.out.printf("0x%x ", b);
     }
    }
}

This may work for very small images. For larger ones, ask/search about "read input stream into byte array"

Now the code I posted works for larger images too.

Answer 3

If you want the byte string as it is stored on disk, just create a socket and open the image file. Then read the bytes as they come down the wire.

I don't have any sample code handy and it's been a while since I've done this, so excuse me if I've got the details wrong to be sure I give this to you straight, but the basic idea would be:

URL imageUrl=new URL("http://someserver.com/somedir/image.jpg");
URLConnection imageConnect=imageUrl.openConnection();
imageConnect.connect();
InputStream is=imageConnect.getInputStream();
... read from the input stream ...