Convert jpeg quality to 80% using automator

Question

I want to make a automator script that goes trough a folder with subfolders and convert all .JPEG (or .JPG) to the same JPEG, but with a quality of 80%.

There is no option in Automator it self like there is in Preview, Pixelmator or Photoshop when saving the JPEG to set the quality. So I installed ImageMagick via homebrew, but I don't know how to pass it functions trough automator.

TL;DR: convert only JPEG in folder with sub folders to a lower quality using automator and don't move the files.

Answer 1

In the imagemagick package there is a program called mogrify that will overwrite the original image file, and another, convert, that will write to a different image file.

In Linux there is another command, find, that will search (and find) all the files in a path that will fullfill the search criteria and that can execute some command with the filename found.

Warning: I strongly suggest to do a backup before starting to use a script that will modify the original files, just to prevent any unpleasant inconvenience that you cannot fix after...

Moreover I suggest you to test the command on a sample (only on some files and not on all).

I understand you want to replace all your images with a lower quality version.
Merging the above two command you can do something similar to

find Path/to/MyFolder -name '*.jpg' -exec mogrify -quality 80 {} \;

Use man mogrify and man find to have some hints more.