You must load it as an image. Do a drawString on the image, then save
it back as a jpeg.  See http://mindprod.com/jgloss/jpegencoder.html
for tools to do the save back.

--
Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

If it already has text on it, you have a problem.  Jpeg text is just
part of the picture.  It is not a separate layer.  You would have to
draw a white box over it then put new text.

You could also use a painting tool to try to get rid of the old text.

See http://mindprod.com/jgloss/psp.html

--
Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

LeiMing:

Here's some sample code:
<http://www.geocities.com/marcoschmidt.geo/java-highlight.html>. It
also colorizes an area, all you need is the graphics.drawString part.

Regards,
Marco