Retain unchanged parts of an image

[keir]

I have a series of images of an object taken on a tripod. People kept moving in and out of the pictures. I would like to take this time series set of pictures and remove the differences.

The command "convert -average" almost does this but leaves "ghosts" of the objects that move in an out of the photo.

How can I preserve those parts of the photo that are constant, removing the changed parts

[fmw42]

You could use compare to find the frame-to-frame difference or -compose difference. Then make those parts transparent and possibly fill the holes.

See
http://www.imagemagick.org/script/compare.php
http://www.imagemagick.org/Usage/compare/
http://www.imagemagick.org/Usage/compose/
http://im.snibgo.com