sun.awt.image.ImageFormatException:
   Unsupported JPEG data precision 12
at sun.awt.image.JPEGImageDecoder.produceImage()

- many medical images (e.g., CT) are 12-bit.
JPEG allows 12-bit compression, e.g.
Processes 4-5, DCT Transform, Huffman or Arithmetic
Coding, 12 bits accepted
or Processes 14-15 and 28-29, DPCM Transform,
2-16 bits accepted.
from ISO/IS-10918-2 (JPEG Part 2)
(Review ID: 26021)
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N/A

I believe Java 2d had JPEG support at one point. I'm assuming it'll go back in once it goes through the public review process.

  xxxxx@xxxxx   1998-06-02
==========================

Its unclear how much demand there is for this feature.
We may or may not address this directly in core, but the Image I/O framework
will certainly allow developers to create a codec to support this.
We will add this to the list of features to be considered for the Image I/O
framework. Closing this as a duplicate of that feature request.

There is a demand in the commercial and DOD community for 
JPEG 12 bit

Most medical images are signed 12-bit JPEG. Java must support them to be even considered for medical imaging use.

This does not work in 1.6.0_12 on both Win and Mac. ComponentColorModel cannot handle signed 12-bit. This issue should NOT be closed.