Printing a Landscape Image

Hey everyone.
So lets say I have a file image.png - a graph. I want to print this graph.

So far I have tried:
lpr -o landscape image.png - this works, but prints the graph on two pages with each half of the graph almost centered in each page...
convert -resize 80% image.png image_t.png; lpr -o landscape image_t.png - this works, but the quality after resizing is very poor.

Long story short - can I print an image that *should* fit on one single page from the command line - and 'force' it to one page if necessary? Do I need to be looking at postcript? Can lpr do this natively?

For completely maintaining the full printing quality, I think you will have to into gs.

But if it is only about that pixel image, try playing around with different filters for convert.
-filter cubic
-filter triangle (especially good for technical drawings)
-filter bicubic

Thanks for the tip! I'll check out convert and see whats up.

do you know of the best way to 'force' the image to be one size? I want lpr to basically keep the image into 1 page.

Firefox so far has been my best option for printing - but its not scriptable.