If you want to resize an image for shortcut icon,or head sculpture,ImageMagick maybe a good choice for you.
ImageMagick is a software suite to create, edit, and compose bitmap images.It supports about 100 image formats and can perform impressive operations such as creating images from scratch.

First,install ImageMagick.Click here if you’re a ubuntu Linux user;If you’re using other system,go to this page for ImageMagick.

After installation,you can resize your images with following codes:

resize an image to 200px width:

mogrify -resize 200 image_name

resize an image to 200*200, with aspect ratio preserved:

mogrify -resize 200*200 image_name

force resize an image to 200*200:

mogrify -resize 200*200! image_name

and resize multiple images with this code:

mogrify -resize 200*200 *.png