If you're looking for a quick and easy bulk image resizing tool, here's a free service I started using a few months ago: bulkresizephotos.com
Simply drag & drop your images into this online tool and the process will start immediately.
Select the reduction percentage (I usually choose 30% when resizing fairly large images, i.e. +/- 3MB per photo).
At the end of the quick bulk image resizing sequence, you'll be prompted to create a destination zip folder for the resized images.
It's that easy!
I've just resized 40 images in less than 5 minutes, reducing their size from +/- 3MB to +/- 250Ko using a 30% reduction rate.
The images are then further processed by a WordPress compression plugin, Bulk Shortpixel, without losing too much quality, while significantly optimising the loading speed of my pages!