<s>[INST] What is a good, free way to scale a large batch of images down? They are of different sizes with the same aspect ratio. The target size is all going to be the same dimensions. [/INST] There are many ways to scale down images in large groups. 
You will may be able to find a free service online that will convert large batches of images, but upload and download times will slow you down. 
I would instead, recommend using a free offline software such as GIMP which works on Windows, Linux and Mac. 

You can download GIMP here:
https://www.gimp.org/downloads/ 

Would you like help installing GIMP on your computer?</s>\ <s>[INST] I said BATCH of images, not one image [/INST] You can use `mogrify` command line tool from ImageMagick for batch image processing: https://imagemagick.org/

The following command resizes all .jpg images of current directory into same target size 1024x768, and store the new images into subfolder "processed":

    magick mogrify -resize 1024x768! -path processed *.jpg

The following command resizes all .jpg and .png images of current directory into 50% of their original sizes, and store the new images one folder up:

    magick mogrify -resize 50% -path .. *.jpg *.png

Be careful that if you do not specify `-path`, the new images will be saved in current directory, overwriting existing files.</s>\ <s>[INST] That worked. Can you put that into a bash script? [/INST] 