[bash - cwebp] Converts all PNG/JPG/JPEG files in a directory (recursive) to WebP. Optional Forced flag to re-convert existing WebP files.

cwebp.sh

#!/bin/bash
# Tested at Debian 10 (Buster)
# Usage: ./cwebp.sh [-f] <directory>

forced=n

# If first arg contains forced flag (-f), remove first arg. Directory becomes first arg.
[ "$1" = "-f" ] && forced=y && shift && echo "Forced Mode Detected"

# List all regular files (JPG/JPEG/PNG) in the directory
# @ -exec:
#   $0 = forced variable ($forced)
#   $1 = File found by find command ({})
# ----------
# cwebp flags should be modified according to your preferences. It's configured to be the 3rd to the best compression.
# [!] Conversion errors are sent to void
#   - cwebp Documentation: https://developers.google.com/speed/webp/docs/cwebp
find $1 -type f -and \( -iname "*.jpg" -o -iname "*.jpeg" -o -iname "*.png" \) \
-exec bash -c '
if [[ "$0" = "y" || ! -f "$1.webp" ]]; then
  echo "Converting $1" && cwebp -short -lossless -z 7 "$1" -o "$1.webp" 2>/dev/null;
fi
' $forced {} \;