How to automate conversion of images

Question

I can convert an image like this:

convert -resize 50% foo.jpg foo_50.jpg

How can I automate such a command to convert all the images in a folder?

You can assume every image has .jpg extension.

A solution easily adaptable to automate the conversion of all the images inside the subdirectories of the working directory is preferable.

Answer 1

You can use a for loop with pattern expansion:

for img in */*.jpg ; do
    convert -resize 50% "$img" "${img%.jpg}"_50.jpg
done

${variable%pattern} removes the pattern from the right side of the $variable.