Question

I’ve been making an image rescaler that uses the ImageIO library in Java to convert them to a buffered image. Unfortunately it doesn’t recognise every type of JPEG that I may pass to it and so I need to “convert” these other types. The way I’m converting them is to take an existing APP0 tag from a standard JFIF JPEG and what I want to do is on the 3rd byte into the file insert 18 bytes of data (the FFE0 marker and the 16 byte APP0 tag) and then I want to add the rest of the file to the end of that.

So to generalise, what’s the most efficient way to add/insert bytes of data mid way through a stream/file?

Thanks in advanced,
Alexei Blue.

This question is linked to a previous question of mine and so I’d like to thank onemasse for the answer given there.
Java JPEG Converter for Odd Image Types

Answer 1

Thanks for the suggestion guys, I used a FilterInputStream at first but then saw there was no need to, I used the following piece of code to enter my APP0 Hex tag in:

private static final String APP0Marker = "FF E0 00 10 4A 46 49 46 00 01 01 01 00 8B 00 8B 00 00";

And in the desired converter method:

        if (isJPEG(path))
        {
            fis = new FileInputStream(path);
            bytes = new byte[(int)(new File(path).length())];
            APP0 = hexStringToByteArray(APP0Marker.replaceAll(" ", ""));

            for (int index = 0; index < bytes.length; index++)
            {
                if (index >= 2 && index <= (2 + APP0.length - 1))
                {
                    b = APP0[index-2];
                }
                else
                {
                    b = (byte) fis.read();
                }//if-else

                bytes[index] = b;
            }//for

            //Write new image file
            out = new FileOutputStream(path);
            out.write(bytes);
            out.flush();
        }//if

Hope this helps anyone having the a similar problem 🙂