Make slideshow GIF from a batch of images using ImageMagick

1. Download and install ImageMagick Mac OS X Binary Release at ImageMagick official site.

   $ tar xvfz ImageMagick-x86_64-apple-darwin12.4.0.tar.gz
   $ export MAGICK_HOME="/YOUR/PATH/TO/ImageMagick-6.8.6"
   $ export PATH="$MAGICK_HOME/bin:$PATH"
   $ export DYLD_LIBRARY_PATH="$MAGICK_HOME/lib/"
   

   See this for installation on Linux.
2. Enter the directory where original images are stored (assuming all files are in .jpg format), use the following command:

   $ convert -delay 100 -loop 0 -resize 300x225 -quality 90 *.jpg image.gif
   

   -deplay represents interval between slides, -loop indicates number of loops for slide show (0 for infinite loops); other options are intuitive. Note that *.jpg will expand to images ordered alphabetically by filename. Use the following command to re-order the images by last modified time:

   $ convert -delay 100 -loop 0 -resize 300x225 -quality 90 `ls -t`