Why two output files?

[Deane]

Last winter I did some greyscale image subtraction using IM (Windows command line box) and wrote down the commands I used.
They worked as expected and output the difference image.
This week I can't make the commands function as expected: I get two files named File-0.jpg and File-1.jpg
Example:
>convert Gray1.jpg Gray2.jpg -compose difference Outfile.jpg

Creates two images: Outfile-0.jpg and Outfile-1.jpg and they look just like the original two images.
What is going on here?
Thanks for any insight on how to get the difference between two images.
Deane

[fmw42]

You did not write the command down fully. You left off the -composite. Try

Code: Select all

convert Gray1.jpg Gray2.jpg -compose difference -composite Outfile.jpg

see http://www.imagemagick.org/Usage/compose/#compose