I'm building a CMS plugin and need an image resize/compress service

Here’s a solid way to think about an image resize/compress service for a CMS plugin, plus a practical implementation outline.

What the service should do

A good image optimization service usually handles:

1. Resize

   • Constrain images to max width/height
   • Preserve aspect ratio
   • Optionally crop or fit within bounds

2. Compress

   • Reduce file size while keeping acceptable visual quality
   • Support per-format settings

3. Format handling

   • JPEG / WebP / PNG / GIF / AVIF if supported
   • Keep transparency for PNG/WebP
   • Avoid quality loss when possible for already-optimized images

4. Metadata cleanup

   • Strip EXIF/IPTC/XMP metadata optionally
   • This helps privacy and reduces size

5. Safety and limits

   • File size limits
   • Dimensions limits
   • Timeout handling
   • Validate MIME type and file extension

6. Non-destructive workflow

   • Preserve original
   • Save optimized copy
   • Generate thumbnails / variants

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Suggested architecture

For a CMS plugin, it’s best to split this into 3 layers:

1) Upload hook

Triggered when media is uploaded.

Responsibilities:

• Validate file
• Queue optimization job
• Save original
• Pass file path/ID to processing

2) Image processor

Does the actual work:

• Read image
• Resize if needed
• Compress/convert
• Save output
• Return metadata

3) Storage/update layer

Handles:

• Replacing attachment metadata
• Updating DB record
• Storing optimization stats
• Keeping backups if enabled

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Recommended processing pipeline

A robust pipeline:

1. Detect image type
2. Load image safely
3. Auto-rotate using EXIF orientation
4. Resize if larger than target max
5. Convert if needed
   • JPEG for photos
   • WebP for smaller size if supported
   • PNG if transparency required
6. Strip metadata if enabled
7. Save optimized file
8. Compare size reduction
9. Replace or store alongside original

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Important implementation details

Resize logic

Use one of these modes:

• Contain: fit inside max width/height without cropping
• Cover: fill exact dimensions, crop edges
• No upscale: never enlarge small images

Example rule:

• Max width: 1920
• Max height: 1080
• If input is 4000x3000, scale down proportionally

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Compression settings

Typical safe defaults:

• JPEG: 75–85
• WebP: 70–80
• PNG: lossless or mild optimization
• AVIF: 40–60 depending on library

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Format conversion strategy

A common policy:

• Photos → JPEG or WebP
• Images with transparency → PNG or WebP
• Animations → preserve GIF/WebP animation if supported
• If converting PNG to JPEG, require a fallback background color

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Tech stack options

If your plugin is PHP-based

Use:

• Imagick if available
• Fallback to GD

Imagick is usually better for:

• Quality
• WebP/AVIF support
• Metadata handling
• Better resizing filters

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Example PHP service structure

You could define a service like this:

class ImageOptimizerService
{
    public function optimize(string $inputPath, array $options = []): array
    {
        $defaults = [
            'max_width' => 1920,
            'max_height' => 1080,
            'quality' => 82,
            'strip_metadata' => true,
            'convert_format' => null, // 'webp', 'jpg', etc.
        ];

        $options = array_merge($defaults, $options);

        $info = getimagesize($inputPath);
        if (!$info) {
            throw new \RuntimeException('Invalid image');
        }

        $mime = $info['mime'];

        // Load image depending on type...
        // Resize if necessary...
        // Compress and save...
        // Return stats...

        return [
            'original_size' => filesize($inputPath),
            'optimized_size' => filesize($outputPath),
            'saved_bytes' => filesize($inputPath) - filesize($outputPath),
            'output_path' => $outputPath,
        ];
    }
}

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Return values you should expose

For CMS integration, return:

• original path
• optimized path
• original dimensions
• new dimensions
• original size
• optimized size
• savings percentage
• output format
• whether metadata was stripped
• any warnings/errors

Example:

{
  "original_size": 2483921,
  "optimized_size": 742188,
  "saved_bytes": 1741733,
  "saved_percent": 70.1,
  "width": 1600,
  "height": 900,
  "format": "webp"
}

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Extra features worth adding

• Bulk optimization
• Background queue
• Duplicate detection
• Image quality presets: low / balanced / high
• Per-folder rules
• Admin preview before replacing originals
• CDN integration
• Logging/auditing

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If you want an API-based service instead

If you don’t want to process images locally, you can expose/use an external service:

• Upload image
• Service returns optimized file URL or binary
• Easier scaling
• But adds latency and cost

Good for:

• Large CMS installs
• Multi-tenant systems
• Server environments without Imagick

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My recommendation

For a CMS plugin, the best default is:

• Local processing
• Imagick first, GD fallback
• Optional WebP output
• Non-destructive originals
• Queue-based bulk optimization
• Configurable size/quality presets

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If you want, I can also provide:

1. a complete PHP class for this service,
2. a WordPress plugin integration example, or
3. an API design for a standalone resize/compress microservice.