Gif2LGTM
Gif2LGTM is a command line tool that generates lgtm images. Not only gif but also png and jpeg are supported.

Installation
First, install the imagemagick. see imagemagick.
$ brew install imagemagick
install it yourself as:
$ gem install gif2lgtm
Usage
Pass the file path to the command. Not only gif but also jpeg and png can be created.
$ gif2lgtm start .gif
Only this. The lgtm-image is generated in the same location as the passed file.
License
The gem is available as open source under the terms of the MIT License.