Compares all images in a directory, duplicates are logged to a file and opened in Preview

image_compare.sh

#!/usr/bin/env zsh

echo "" > _compare.txt
THRESHOLD=0.05

# Find similar images in a directory
for file1 in *.png; do
    echo -n "."
    for file2 in *.png; do
        if [ "$file1" != "$file2" ]; then
            # Run comparison in background
            (
                # Lower RMSE means more similar images
                similarity=$(compare -metric AE "$file1" "$file2" null: 2>&1)
                
                # Extract just the numeric value, handling both possible output formats
                similarity_float=$(echo "$similarity" | sed 's/[()]//g' | awk '{print $1}')
                
                # Check if similarity_float is actually a number and compare
                if [[ "$similarity_float" =~ ^[0-9]*\.?[0-9]+$ ]]; then
                    result=$(echo "$similarity_float < $THRESHOLD" | bc 2>/dev/null)
                    if [ "$result" -eq 1 ]; then
                        echo -n "#"
                        echo "$file1" >> _compare.txt
                        echo "$file2" >> _compare.txt
                        echo "" >> _compare.txt
                        open "$file1" "$file2"
                    fi
                fi
            ) &
        fi
    done
done

wait
echo "Comparison complete"

by Matt Sephton, March 2025, MIT