If you insert a large graphic image into Impress, and then reduce it in size,
the image looks bad.  If you do the same with Powerpoint, it looks good.  
This is a pain because it means you must generate any image at the desired
resolution.  I would like to generate one 600dpi image and use it for printing
or in OpenOffice.

I am attaching a large image.  For example, the bottom graph has thin gray
horizontal lines in the background.  Using Powerpoint, you can see all the lines
at any scale, or you can see none of them.  With OOO, you can often see only a
subset of the lines.

Libart (LGPL) has some image reduction algorithms.  This file mentions some:
http://cvs.gnome.org/bonsai/cvsblame.cgi?file=libart_lgpl/art_filterlevel.h&rev=&root=/cvs/gnome

Under Linux, GQView allows you to select several different reduction algorithms,
(which I think come from libart through GNOME).  Load GQview and go to
Edit->Options->Image->Zoom(scaling).  When I select 'Hyper', the reduced image
looks great.  

Would it be possible to implement the 'Hyper' algorithm for rescaling?
(art_filterlevel.h above says:
It is derived from the hyperbolic filters in Wolberg's "Digital Image Warping,"
and is formally defined as the hyperbolic-filter sampling the ideal
hyperbolic-filter interpolated image (the filter is designed to be
idempotent for 1:1 pixel mapping).
)