Simple `imagemagick` fish shell script to convert all @2x images in a directory to @1x. Place file in `~/.config/fish/functions/`, then run like normal: `resize`!

resize.fish

function resize --description "Resize images from @2x to @1x in current directory."
  for image in *
    echo $image | grep -qE '.*@2x.*'; and \
      convert $image -resize 50% (echo $image | sed "s/@2x/@1x/g")
  end
end