Java image and byte[]

Question

I am having trouble writing and reading data from an image. I am using the following code to get the bytes for a picture.
BufferedImage pic = ImageIO.read(new File(picture));
WritableRaster writableRaster = pic.getRaster();
DataBufferByte buffer = (DataBufferByte)writableRaster.getDataBuffer();
byte[] picBytes = buffer.getData();After making some changes I would like to write the new bytes to a file. This seems to work as the new picture shows the changes when I look at it.
File newFile = new File("C:/NewPic.jpg");
ImageIO.write(pic,"jpg",newFile);However, when I try to read the newFile using the same method as above I do not get the same bytes. I am using the following code to print the bytes in hex to verify what they are.
BufferedWriter out2 = new BufferedWriter(new FileWriter("pix2.txt"));
for(int x=0; x<picBytes.length; x++)
out2.write((Integer.toString(picBytes[x] & 0xff, 16).toUpperCase()+" "));
}This produces:
7F 7F 7F 7F 7F 7F 7F 7F 7F 7F 7F 7F 7F 7F 7F 7F
7F 7F 7F 7F 7F 7F 7F 7F 7F 7F FF FF 7F FF FF FF
for the bytes that I have made the changes to, and when I try to read from the newly created file I get:
82 7F 7A 82 7F 7A 82 7E 7D 82 7E 7D 82 7D 7F 82
7D 7F 82 7B 82 82 7B 82 AC A5 AC B4 AE B3 E0 DA
but there is nothing wrong with the picture. Do I need to create a new BufferedImage before I save, or what could be causing this change?

Answer 1

Hmmm... I'm not sure what you are doing or what your goal is, but are you aware that JPEGs tend to use a losey compression?