"Bogus marker length" exception when jpeg save

Question

I wrote a program to modified jpeg bytes. Actually quantization tables. But when I save image, I'm getting an IIOException: Bogus marker length.
InputStream in = new ByteArrayInputStream(b);
BufferedImage bImageFromConvert = ImageIO.read(in);
ImageIO.write(bImageFromConvert, "jpg", new File(fname));b - is a byte array, I got it by using toByteArray():
BufferedImage img = ImageIO.read(new File(filename));
ByteArrayOutputStream baos = new ByteArrayOutputStream();
JPEGImageEncoder en = JPEGCodec.createJPEGEncoder(baos);
en.encode(img);
b = baos.toByteArray();then I modified some bytes. But not markers! and I don't add any extra bytes...
Exception is:
javax.imageio.IIOException: Bogus marker length
at com.sun.imageio.plugins.jpeg.JPEGImageReader.readImageHeader(Native Method)
at com.sun.imageio.plugins.jpeg.JPEGImageReader.readNativeHeader(JPEGImageReader.java:517)
at com.sun.imageio.plugins.jpeg.JPEGImageReader.checkTablesOnly(JPEGImageReader.java:272)
at com.sun.imageio.plugins.jpeg.JPEGImageReader.gotoImage(JPEGImageReader.java:394)
at com.sun.imageio.plugins.jpeg.JPEGImageReader.readHeader(JPEGImageReader.java:510)
at com.sun.imageio.plugins.jpeg.JPEGImageReader.readInternal(JPEGImageReader.java:913)
at com.sun.imageio.plugins.jpeg.JPEGImageReader.read(JPEGImageReader.java:897)
at javax.imageio.ImageIO.read(ImageIO.java:1422)
at javax.imageio.ImageIO.read(ImageIO.java:1326)
Could somebody help me, please?

Answer 1

Well, the problem is in your code with 99,99% probability.
I'd probably start debugging this by first just reading and saving the file directly, without any modifications (but go through the conversion to byte array).
That should definitely work, but if it doesn't then your byte handling is the problem.
Then I'd add simple modifications incrementally to see where it goes wrong.