$ file MyPNG.png
$ convert MyJpeg.jpg -print "Size: %wx%h\n" /dev/null

convert example.png -resize 200×100 example.png

Install librsvg2-bin

• http://www.howtogeek.com/109369/how-to-quickly-resize-convert-modify-images-from-the-linux-terminal
• http://superuser.com/questions/275502/how-to-get-information-about-an-image-picture-from-the-linux-command-line