Reduce the original product image size to 1000×1000 dimension in Magento 2

Use imagemagick.

for f in find . -name "*.jpg"
do
convert $f -resize 50% $f.resized.jpg
done

For finding the files to resize, you can use xargs. Example:

find . -name “*.jpg” | xargs convert -resize 50%

This will create copies of the images. If you just want to convert them in place, you can use:

find . -name “*.jpg” | xargs mogrify -resize 50%