pad a directory of images to 1:1 aspect ratio (overwriting original files)

pad_square.sh

#!/bin/bash
# use `-format png` to change output format, converting files at the same time, but then perhaps consider changing the final $img in line 12 to somethingelse_$img
for img in *.jpg *.jpeg *.png; do
  if [ -f "$img" ]; then
    width=$(identify -format "%w" "$img" 2>/dev/null)
    height=$(identify -format "%h" "$img" 2>/dev/null)
    if [ -z "$width" ] || [ -z "$height" ]; then
      echo "Skipping $img (not a valid image)"
      continue
    fi
    size=$((width > height ? width : height))
    convert "$img" -gravity center -background white -extent "${size}x${size}" "$img"
    echo "Padded $img to ${size}x${size}"
  fi
done