A Bash script for adding a watermark to all image files (.png, .jpg, .jpeg) in a specified directory.

watermark.sh

#!/bin/bash

# Check the number of arguments
if [ "$#" -ne 3 ]; then
    echo "Usage: $0 <path to watermark image> <search location> <dissolve percentage>"
    exit 1
fi

# Path to the watermark image
watermark_path="$1"

# Search location
search_location="$2"

# Dissolve percentage for transparency
dissolve_percentage="$3"
if ! [[ "$dissolve_percentage" =~ ^[0-9]+$ ]]; then
  echo "Dissolve percentage must be a number"
  exit 1
fi
if [ "$dissolve_percentage" -lt 0 ] || [ "$dissolve_percentage" -gt 100 ]; then
  echo "Dissolve percentage must be between 0 and 100"
  exit 1
fi

# Iterate over all image files in the directory
find "$search_location" -type f \( -iname "*.png" -o -iname "*.jpg" -o -iname "*.jpeg" \) -print0 | while IFS= read -r -d '' file; do
  # Get the filename and extension
  filename="${file%.*}"
  extension="${file##*.}"

  # Add a watermark to the image
  magick composite -dissolve "$dissolve_percentage" -gravity southwest -geometry +15+15 "$watermark_path" "$file" "$filename"_wm.$extension

  if [ $? -ne 0 ]; then
    echo "Failed to watermark $file" >> wm.log
  else 
    echo "Watermarked $file, output to $filename"_wm.$extension""
  fi
done