How It Works - Technical Deep Dive
Understanding the technology behind ImageToPDF's client-side image and PDF processing
Core Technology Stack
Client-Side JavaScript Libraries
jsPDF
Used for creating PDF documents from images. This library generates PDFs entirely in the browser without any server communication.
PDF.js (Mozilla)
Used for reading and extracting images from PDF files. PDF.js is the same rendering engine used in Firefox's built-in PDF viewer.
Canvas API
Native browser API used for image manipulation, format conversion, and rendering PDF pages to images.
Image to PDF Conversion Process
File Selection
User selects image files using the file input or drag-and-drop. Files are accessed via the FileReader API, which reads them as Data URLs.
Image Loading
Images are loaded into HTMLImageElement objects to extract dimensions and pixel data. EXIF orientation data is read to handle rotated photos correctly.
PDF Generation (Web Worker)
Image data is transferred to a Web Worker to avoid blocking the main thread. The worker uses jsPDF to create pages and embed images with specified quality and layout settings.
Download
The generated PDF is converted to a Blob, a temporary download URL is created with URL.createObjectURL(), and downloaded via a virtual anchor element.
PDF to Image Extraction Process
PDF Loading
PDF file is read as an ArrayBuffer and loaded into PDF.js using getDocument(). This parses the PDF structure and metadata.
Page Selection
User can choose to extract all pages or specific page ranges. Pages are processed individually to conserve memory.
Chunked Rendering
For large PDFs (100+ pages), pages are processed in chunks of 10 with small delays between chunks. This prevents browser memory exhaustion and UI freezing.
Canvas Rendering
Each PDF page is rendered to an HTML5 Canvas at the specified DPI (scale). The canvas is then converted to PNG/JPG using canvas.toBlob().
Performance Optimizations
⚡ Web Workers
Heavy PDF generation runs in background threads, keeping the UI responsive during conversions.
Prevents browser "Not Responding" warnings
📦 Lazy Loading
jsPDF and PDF.js are loaded on-demand using dynamic imports, reducing initial page load time.
Libraries only load when user starts conversion
🧩 Chunked Processing
Large PDF files are processed in small batches with intervals, preventing memory overload.
Handles documents with 1000+ pages
🧹 Memory Cleanup
Blob URLs are explicitly revoked after downloads to prevent memory leaks during batch processing.
Memory usage monitored in real-time
Privacy & Security Architecture
🔒 Zero Server Communication
All file processing happens entirely in your browser using JavaScript. No files, metadata, or analytics are sent to any server.
No file uploads: Files are read directly from your device using the FileReader API
No external libraries from CDNs: All libraries are bundled and served from our domain
No cookies or tracking: No user identification or behavior tracking mechanisms
Automatic memory cleanup: All file data is cleared from browser memory after conversion
Browser Compatibility
| Browser | Minimum Version | Status |
|---|---|---|
| Chrome / Edge | Version 90+ | ✓ Fully Supported |
| Firefox | Version 88+ | ✓ Fully Supported |
| Safari | Version 14+ | ✓ Fully Supported |
| Mobile Safari (iOS) | iOS 14+ | ✓ Fully Supported |
| Chrome Mobile (Android) | Android 90+ | ✓ Fully Supported |
Required APIs: FileReader, Canvas, Blob, Web Workers, Dynamic Imports (ES2020)
Known Limitations
Browser Memory Limits
Most browsers limit JavaScript memory to 1-2 GB. Processing very large files (>500 MB total) may cause browser crashes. Use smaller batches for best results.
Complex PDF Features
Advanced PDF features like forms, annotations, digital signatures, and encrypted PDFs are not fully supported. Focus is on image extraction and simple image-to-PDF conversion.
Format-Specific Limitations
HEIC format requires browser support or polyfill. Some older browsers may not support WebP. SVG files are rasterized when converted to PDF (vector information is not preserved).
Open Source Technology
ImageToPDF is built on open-source foundations:
- •jsPDF: MIT License - Client-side PDF generation
- •PDF.js: Apache 2.0 License - Mozilla's PDF rendering library
- •Nuxt: MIT License - Vue.js framework for server-side rendering