Image Resizer Script for Raspberry Pi OS

A robust shell script for batch resizing images to multiple dimensions while maintaining aspect ratios. Perfect for creating responsive image sets for web development or photo galleries.

Features

• Batch Processing: Automatically processes all JPG, JPEG, and PNG files in a directory
• Smart Resizing: Creates three resized versions (480px, 720px, 1280px max dimension) while maintaining aspect ratios
• Duplicate Protection: Skips already processed files and prevents re-processing of output files
• File Validation: Automatically detects and skips corrupted or invalid image files
• Format Preservation: Maintains original file formats with proper case handling
• Auto Dependency Management: Automatically checks for and installs FFmpeg if needed

Requirements

• Raspberry Pi OS (latest recommended)
• Internet connection (for initial FFmpeg installation)

Installation

1. Download the script:

   wget https://raw.githubusercontent.com/Stryfe-Delivery/image-repository-manager/main/image-converter.sh

2. Make it executable:

   chmod +x image-converter.sh

3. Run directly or move to a directory in your PATH:

   # For system-wide access:
   sudo mv image-converter.sh /usr/local/bin/image-resizer

Usage

Basic Usage

# Navigate to your image directory
cd /path/to/your/images

# Run the script
./image-converter.sh

What It Does

For each valid image file (e.g., photo.jpg), the script creates three resized copies:

• photo-400.jpg (480px max dimension)
• photo-800.jpg (720px max dimension)
• photo-1200.jpg (1280px max dimension)

Original files are never modified or deleted.

File Validation

The script includes built-in file validation that automatically detects and skips:

• Corrupted image files
• Files with incorrect extensions
• Non-image files with image extensions

Manual File Validation Check

If you want to manually check for invalid PNG files before running the script, use this grep command:

# Check for invalid PNG files in the current directory
file *.png */*.png 2>/dev/null | grep -v "PNG image"

# For a more comprehensive check including all image types:
find . -type f \( -iname "*.png" -o -iname "*.jpg" -o -iname "*.jpeg" \) -exec file {} \; | grep -vE "(JPEG image|PNG image|JPEG|PNG)"

Understanding the Grep Check

file *.png */*.png 2>/dev/null | grep -v "PNG image"

• file *.{png,PNG}: Uses the file command to detect actual file types (not just extensions)
• 2>/dev/null: Suppresses error messages for non-existent files
• grep -v "PNG image": Shows only files that are NOT valid PNG images
• The -v flag inverts the match, displaying lines that don't contain "PNG image"

This helps identify files that have .png extensions but aren't actually valid PNG images, which could cause processing errors.

Output Examples

Input files:

vacation.jpg
family.png
document.pdf  # Skipped - not an image
corrupted.png # Skipped - invalid image file

Output files:

vacation.jpg          # Original preserved
vacation-400.jpg      # 480px max dimension
vacation-800.jpg      # 720px max dimension  
vacation-1200.jpg     # 1280px max dimension
family.png            # Original preserved
family-400.png        # 480px max dimension
family-800.png        # 720px max dimension
family-1200.png       # 1280px max dimension

Troubleshooting

Common Issues

1. Permission Denied

   chmod +x image-converter.sh

2. FFmpeg Installation Fails

   sudo apt update && sudo apt install ffmpeg

3. Invalid PNG Files

   • Use the grep check above to identify problematic files
   • Consider re-downloading or re-saving corrupted images

4. Script Not Found

   # Ensure you're in the correct directory or use full path
   /path/to/script/image-converter.sh

Logging

The script provides detailed output showing:

• Which files are being processed
• Which files are skipped (already processed or invalid)
• Success/failure status for each conversion
• Warnings for invalid image files

Customization

You can modify the script to change:

• Output dimensions (edit the convert_image function)
• File suffixes (update the -400, -800, -1200 patterns)
• Supported file types (modify the find command patterns) These patterns are specficially needed for a website hosting repo being devloped.

Contributing

Contributions are welcome! Please feel free to submit pull requests or open issues for bugs and feature requests.

Support

If you encounter any issues:

1. Check the troubleshooting section above
2. Ensure all files have correct permissions
3. Verify FFmpeg is properly installed: ffmpeg -version
4. Run the file validation check to identify problematic images
5. Feel free to reach out (just be patient and nice please)

---

Note: Always test the script on a copy of your images before processing important files.