How PicConverter Works

1. You drop an image

When you drag a file (or pick one from the file dialog), the browser reads it into memory as a raw byte buffer using the File API. No network request is made — the data stays entirely on your device.

2. WebAssembly takes over

PicConverter ships a copy of libvips — the same high-performance imaging library used by Sharp, Cloudinary and imgproxy — compiled to WebAssembly (Wasm). On first load the ~3 MB Wasm binary is fetched and cached by your browser. After that it works offline.

3. Decode → Transform → Encode

Inside the Wasm worker three things happen in sequence:

1. Decode — the source bytes are parsed into a pixel buffer. Supports JPEG, PNG, WebP, AVIF, HEIC, HEIF, TIFF, GIF, JPEG XL, SVG and BMP.
2. Transform — the pixel buffer is rotated, flipped, resized and/or stripped of metadata according to your settings. Resizing uses the Lanczos3 kernel for the sharpest results.
3. Encode — the buffer is written out in the target format (JPEG, PNG, WebP, AVIF, GIF, TIFF, BMP, SVG or JPEG XL) at your chosen quality. SVG output uses image tracing (vtracer) to convert pixels into vector paths.

4. Web Worker isolation

The heavy lifting runs inside a Web Worker — a background thread that cannot access the DOM. This keeps the UI responsive even while converting large images or processing a batch. The worker communicates with the main thread via postMessage using transferable byte buffers for zero-copy performance.

5. Download the result

Once encoded, the output blob is handed back to the main thread. You can download files individually or, for batch conversions, as a single ZIP created client-side with JSZip. Again — nothing ever leaves your machine.

Architecture at a glance

Everything above happens inside your browser. Zero network traffic.

Why this matters for privacy

• No server can be breached because no server ever receives your images.
• Works on air-gapped machines and behind strict firewalls.
• Once the page loads, you can disconnect from the internet entirely.