Im Resizer - WordPress Image Optimization Plugin

A powerful WordPress plugin to automatically resize images on upload and batch process existing images to save hosting space.

Features

• Auto Resize on Upload: Toggle to automatically resize images when uploaded to WordPress media library
• Batch Processing: Scan and process all images in your uploads directory
• PHP-FPM Optimized: Configurable delays and request limiting to prevent server overload
• Configurable Settings:
  • Set maximum width and height
  • Adjust JPEG quality
  • Configure batch processing size (5-50 images per batch)
  • Set delay between batches (1-10 seconds)
  • Limit concurrent requests (1-3, default: 1)
• Real-time Processing Log: See exactly what's happening with each image
• Smart Scanning: Recursively scans all subdirectories for images
• Multiple Image Formats: Supports JPG, JPEG, PNG, BMP, and GIF
• No Timeouts: Processes images in batches to prevent script timeouts
• Memory Efficient: Optimized to handle large image libraries
• Error Handling: Continues processing even if individual images fail
• Overwrites Originals: Saves hosting space by not keeping backups
• Request Locking: Prevents concurrent processing to protect server resources

Installation

Method 1: Manual Upload

1. Download the plugin files
2. Create a folder named im-resizer in your /wp-content/plugins/ directory
3. Upload all plugin files to /wp-content/plugins/im-resizer/
4. Go to WordPress Admin → Plugins
5. Activate "Im Resizer"

Method 2: ZIP Upload

1. Package all files into a ZIP file named im-resizer.zip
2. Go to WordPress Admin → Plugins → Add New
3. Click "Upload Plugin"
4. Choose the ZIP file and click "Install Now"
5. Activate the plugin

File Structure

im-resizer/
├── im-resizer.php      # Main plugin file
├── js/
│   └── admin.js        # Admin JavaScript
├── css/
│   └── admin.css       # Admin styles
└── README.md           # This file

Usage

Initial Setup

1. Go to WordPress Admin → Im Resizer

2. Configure your settings:

   • Max Width: Maximum image width in pixels (default: 1920)
   • Max Height: Maximum image height in pixels (default: 1920)
   • JPEG Quality: Compression quality 1-100 (default: 85)
   • Batch Size: How many images to process at once (default: 20)
   • Auto Resize on Upload: Toggle ON to automatically resize new uploads

3. Click "Save Settings"

Batch Processing Existing Images

1. Click the "Scan Images" button

   • Plugin will scan all folders and subfolders
   • Shows total images found
   • Shows how many need resizing
   • Displays total size of oversized images

2. Review the scan results in the stats panel

3. Click the "Process Images" button

   • Processes images in batches
   • Shows real-time log of each image processed
   • Displays original and new dimensions/sizes
   • Shows progress percentage
   • Updates processed/failed counters

4. Use "Stop Processing" button to pause processing after current batch

Real-time Log

The processing log shows:

• Timestamp of each action
• Filename being processed
• Original dimensions and file size
• New dimensions and file size
• Success/failure status with color coding:
  • Green: Successfully processed
  • Red: Failed to process
  • Orange: Warnings
  • Blue: Information messages

Technical Details

Image Processing

• Uses PHP GD library for image manipulation
• Maintains aspect ratio when resizing
• Preserves transparency for PNG and GIF images
• Supports JPEG, PNG, GIF, and BMP formats
• Overwrites original files (no backups created)

Performance

• Processes images in configurable batches (10-100)
• Sets unlimited execution time to prevent timeouts
• Increases memory limit to 512MB for processing
• Small delays between batches to prevent server overload
• Continues processing even if individual images fail

Security

• Nonce verification for all AJAX requests
• Capability checks (requires 'manage_options')
• Sanitized and validated inputs
• Escapes all outputs

Settings Explained

Max Width/Height

The maximum dimensions for any image. Images larger than these dimensions will be proportionally resized to fit within these limits while maintaining aspect ratio.

JPEG Quality

Compression quality for JPEG images:

• 1-40: Low quality, small file size
• 50-70: Medium quality, balanced
• 80-95: High quality, larger file size
• 96-100: Maximum quality, minimal compression

Batch Size

Number of images to process in each batch:

• Smaller (5-10): Best for limited server resources and low PHP-FPM limits
• Medium (15-20): Good balance for most servers
• Larger (30-50): Faster processing on powerful servers

Important for PHP-FPM: Keep this lower (5-15) if your server has PHP-FPM limits of 5 or fewer processes.

Batch Delay

Time to wait between processing batches:

• 1 second: Faster processing, more server load
• 2-3 seconds: Recommended for most servers
• 5-10 seconds: Safest for servers with strict resource limits

Critical for PHP-FPM: This delay ensures your server doesn't hit PHP-FPM process limits. With a 2-3 second delay and batch size of 10, the plugin will never exceed 1-2 concurrent PHP-FPM processes.

Max Concurrent Requests

Maximum number of simultaneous processing requests:

• 1 (Safest): Only one batch processes at a time - Recommended for PHP-FPM limit of 5
• 2: Two batches can process simultaneously
• 3: Three batches can process simultaneously

For PHP-FPM servers: Always keep this at 1 to ensure you never exceed your PHP-FPM process limit. The plugin uses request locking to enforce this limit.

Auto Resize on Upload

When enabled:

• Automatically resizes images when uploaded to media library
• Applies settings immediately on upload
• Saves hosting space from the start
• No need to batch process new uploads

PHP-FPM Optimization

Why These Settings Matter

If your server has a PHP-FPM limit (commonly 5-10 processes), aggressive batch processing can exhaust all available PHP-FPM workers, causing:

• Website slowdown or unavailability
• 502/504 errors for other users
• Failed batch processing

Recommended Settings for PHP-FPM Limit of 5:

• Batch Size: 10-15 images
• Batch Delay: 2-3 seconds
• Max Concurrent Requests: 1 (enforced by default)

This ensures:

• Each batch uses only 1 PHP-FPM process
• 2-3 second gaps allow other requests to process
• Website remains responsive during batch processing
• No PHP-FPM pool exhaustion

How It Works:

1. Request Locking: PHP transient locks prevent concurrent batch processing
2. JavaScript Queue: Only one AJAX request processes at a time
3. Configurable Delays: Waits between batches to free up PHP-FPM workers
4. Small Image Delays: 0.1 second pause between individual images in a batch

Troubleshooting

Images not processing

• Check PHP GD library is installed (php -m | grep gd)
• Verify file permissions (files should be writable)
• Increase batch size to smaller number
• Check error log for specific issues

Script timeout

• Plugin is designed to prevent timeouts
• If still occurring, reduce batch size
• Check PHP max_execution_time setting

Memory issues

• Plugin increases memory to 512MB
• If still failing, increase batch size to smaller number
• Check server memory limits

Images look bad quality

• Increase JPEG Quality setting (try 90-95)
• PNG/GIF quality is always maximum

Requirements

• WordPress 5.0 or higher
• PHP 7.4 or higher
• PHP GD library installed
• Write permissions on uploads directory

Support

For issues or feature requests, contact the developer or check the plugin documentation.

Version History

1.0.0

• Initial release
• Auto resize on upload
• Batch scanning and processing
• Real-time processing log
• Support for JPG, PNG, GIF, BMP
• Configurable settings
• No timeout processing
• PHP-FPM optimization features:
  • Request locking to prevent concurrent processing
  • Configurable batch delays (1-10 seconds)
  • Adjustable batch sizes (5-50 images)
  • Max concurrent request limiting
  • JavaScript request queue system
  • Server-side transient locks
  • 0.1 second delays between individual images

License

GPL v2 or later

Author

SS - WordPress Developer

• Website: https://masterkey.bm
• Advanced site: https://advanced.bm

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Important Notes:

1. This plugin overwrites original images without creating backups. Make sure you have a backup of your media library before running batch processing for the first time.
2. For servers with PHP-FPM limits: Use the recommended settings (Batch Size: 10-15, Batch Delay: 2-3 seconds, Max Concurrent: 1) to prevent server overload and maintain website availability during processing.