Is it possible to resize images from command line?

I'd like to know how to resize images in ubuntu Which is the easiest tool to use?

First install ImageMagick via.

sudo apt-get install imagemagick

Open a terminal and run this command

convert  -resize 20% source.png dest.jpg

It will reduce the size to 20%.
Note that the reduction is not by 20%.
The resulting image will be much smaller, 20% of the former size,
not 20% smaller than before, not much smaller.

You can also specify the size

convert -resize 1024X768  source.png dest.jpg

You can also use: mogrify command-line tool from the same package.