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.
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