Image resizing - losing detail with some color combinations

Hi list,

I have noticed that when I rescale an image using with-graphics-scale some
foreground/background colour combinations result in loss of detail. Bitmap
resizing inevitably results in some loss of resolution, of course, but I'm
noticing it more strongly with certain colours. For instance if a certain detail
is reduced to a line a single pixel in width then with a green foreground and
black background I lose it, whereas a white background and blue foreground will
show it clearly. The images in question are derived via make-image-from-port, so
I'm stuck with bitmaps.

Any thoughts/suggestions?

Thanks in advance,
Chris