ImageMagick

convert

convert -geometry 100 foo.jpg foo2.jpg # (width)
convert -geometry x100 foo.jpg foo2.jpg # (height)
$ for i in *.JPG; do convert -geometry 100 $i t/$i; done

EXIF (identify)

http://www.imagemagick.org/script/command-line-options.php#format

identify -format "%[EXIF:*]" foo.jpg
identify -format "%[EXIF:DateTimeOriginal]" foo.jpg