Posted: 2006-05-24T10:05:44-07:00
You can try the -median option to filter noise. If you add +dither before your -monochrome option, you may not get the noise to begin with.
The 1x1 pixels will be points what the two background images vary.
Also if you include the URL's for the images we may be able to see just what you are attempting and give alturnative solutions.