Batch resize images and output images to new folder with ImageMagick

"Mogrify" should be called from the directory with the original thumbnails, while the -path parameter is for pointing target directory.

mkdir public_html/images/new-thumbs
cd public_html/images/thumbs
magick mogrify -resize 16x12 -quality 100 -path ../new-thumbs *.jpg

http://www.imagemagick.org/Usage/basics/#mogrify

The last arguments are the list of files, so you can filter by name 1-*.jpg for example.

For those having Shotwell installed on Ubuntu/Debian, following may be more easy to export selected images in a folder to another folder through processing the images as needed.

• Open Shotwell
• Select the images you want to export
• File > Export
• Adjust the values to your needs
• Select the folder to export

In ImageMagick 7 versions its built into the magick ...so..

magick mogrify -resize 16x12 -quality 100 -path ../new-thumbs *.jpg

Make sure that the folder you specify in path exists. It will not be created by ImageMagick.

Find more information here https://www.imagemagick.org/script/mogrify.php

Suggested solutions do not work properly on the latest ImageMagick (at least, on macOS). Command, that works overwriting source images is as follows:

magick mogrify -path ./ -resize 50% -quality 80 *.jpg

To avoid overwriting the original images, write to a new folder:

magick mogrify -path path/to/destination/folder/ -resize 50% -quality 80 *.jpg