jpg with less than 24 bit color

[Liz]

I have
BufferedImage I;
that I write to a file as a jpg using
FileOutputStream fos = new FileOutputStream("filename");
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(fos);
encoder.encode(I);
This creates 24 bit color, but my Image only uses a few
colors. How can I create a jpg with say 4 or 8 bit color.

 

[ak]

This creates 24 bit color, but my Image only uses a few

colors. How can I create a jpg with say 4 or 8 bit color.

8 bit jpeg are greyscale.
use gif.