Tip Of The Day (2) : Batch resizing pictures in linux

How to batch resize pictures in Linux (Mint and Ubuntu based distros)

Don't forget to read the other tips:

Tip Of The Day (5) : Batch Script to resize pictures in linux (Nemo)

Tip Of The Day (4) : Bulk renaming files in linux

Tip Of The Day (3) : Linux Mint 13 and Petra Backports

Tip Of The Day (1) : Screenshot 

first install imagemagick : 
sudo apt-get install imagemagick

then open in terminal the folder containing your pictures you want to resize, and then type the following : 
for file in *.[picture extension]; do convert $file -resize [size you want] [new-name]-$file; done

example, for .JPG files that you want to resize in 800*600 (the file will be sized to fit in a 800*600 frame without destroying ratio)
for file in *.JPG; do convert $file -resize 800x600 resized-$file; done

Your resized pictures are now called resized-*.JPG (original pics are not overwritten) ie : 
DSCF2248.JPG is now called resized-DSCF2248.JPG

Now you have forum-ready pics, for fast upload and quick sharing ;)

That's all folks !