Imagemagick, mass resize photos

I use Imagemagick when I have a lot of pictures that need to be resized for being used on a website. From a shell, the command for resize a picture is: $ mogrify -resize <width_pixel>x<height_pixel> file.jpg For resize all pictures inside a folder, via shell move to the folder and give: $ mogrify -resize <width_pixel>x<height_pixel> * Some time pictures are in more sub-folder, and is not very...