Requirement
Installation
Debian/Ubuntu
sudo apt-get install imagemagick
MacOS/Brew
brew install ghostscript
brew install imagemagick
Solution
Execute this in this directory with the images you want to resize. Do not forget to create a small-jpgs directory
before.
mogrify -path ../small-jpgs -resize 30% *
It is also possible to reduce the quality by adding -quality 90 for example.
mogrify -path ../small-jpgs -quality 90 -resize 30% *
And if you want, you can even change the image format with -format jpg.
mogrify -path ../small-jpgs -quality 90 -format jpg -resize 30% *