Image Compression

Overview

The image compression module automatically optimizes uploaded images before they are stored or printed. This ensures consistent file sizes and faster upload/download times.

Default Settings

Parameter	Default Value	Description
maxWidth	800px	Maximum image width
maxHeight	800px	Maximum image height
quality	0.7 (70%)	JPEG compression quality
maxSizeBytes	500KB (512,000 bytes)	Target maximum file size

API Functions

Function	Parameters	Returns	Description
compressImage(file, options?)	File/Blob, optional CompressOptions	Promise<Blob>	Compress image with options
fileToDataUrl(file)	File/Blob	Promise<string>	Convert file to base64 data URL
compressAndConvertToDataUrl(file, options?)	File/Blob, optional CompressOptions	Promise<string>	Compress and return data URL
resizeDataUrl(dataUrl, maxWidth?, maxHeight?)	dataUrl string, optional dimensions	Promise<string>	Resize existing data URL

Compression Algorithm

1. Load image into memory
2. Calculate resize ratio if dimensions exceed maxWidth/maxHeight
3. Draw to canvas at target dimensions
4. Export as JPEG blob at specified quality
5. If result exceeds maxSizeBytes, recursively reduce quality by 0.1

Usage Locations

• Image Upload: apps/web/routes/image-upload.tsx - compresses before session storage
• Gallery Selection: Compresses selected images before storing
• Final Generation: CollageProvider uses for preparing print output

Code Reference

• Library: apps/web/lib/image-compression.ts
• Integration: Used by providers/collage-provider.tsx for final image generation

Configuration Options

interface CompressOptions {
  maxWidth?: number;      // Max width in pixels
  maxHeight?: number;     // Max height in pixels
  quality?: number;       // 0.0 to 1.0
  maxSizeBytes?: number;  // Target max file size
}

Key Implementation Details

• Uses HTML5 Canvas API for resizing
• Recursive quality reduction ensures target size is met (minimum quality: 0.1)
• Supports both File objects (from input) and Blob objects
• Output format is always JPEG for optimal compression