Keeping the size of a screenshot for XML->FO->PDF transformation

Hello,

(Sorry, I sent the previous message to the wrong list)

I tried to find an answer to the following problem on mailing-list archives
and using google but with no success.
 
I have several screenshots in PNG format. When I generate the PDF file
(using FOP) the small screenshots appear a lot larger than the original
files. Not only it takes too much space, but also the text is fuzzy.
I tried using the different attributes for imagedata (width, depth,
contentdepth, contentwidth ..) but the output is always the same.
I would like the graphic to always be the same size as the original.
What should I do?
 
Diane Larin
INRO