The φCoherent image codec is lossless: it shrinks an image with no change to a single pixel. Here it runs in your browser against an optimized PNG, the universal lossless image format, on the exact same pixels. Pick a photo or drop in your own, then compare the decoded reconstruction to the original and see for yourself that nothing was lost.
Everything runs locally via WebAssembly. Nothing you load is uploaded. The PNG baseline is fully optimized (adaptive filtering, maximal deflate), not the browser's weaker default, so the comparison is fair. On the Kodak and CLIC photographic corpora the φ codec is around 30% smaller than an optimized PNG and a few percent smaller than WebP-lossless. It trades encode speed for ratio.
No image yet. Pick a photo above, or drop in your own.
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The .pei is the φ‑compressed file; it opens only with the φ codec. The decoded PNG is the bit‑identical reconstruction, so you can compare it to your original outside the browser.
The φ result is computed live in phi-compress-image (WebAssembly), the same codec we ship, at quality 1 (lossless). The PNG baseline is encoded in your own browser from the identical pixels with UPNG.js (adaptive per-row filtering and maximal deflate); it is a fully lossless, optimized PNG that lands within a few percent of optipng and zopflipng, well below the browser's default canvas.toBlob PNG. Sizes are the compressed payload for each codec versus the raw RGB pixels. Large images are scaled to fit before encoding so the demo stays responsive. The φ codec is optimized for size, not throughput. Sample photos are from the Unsplash and CLIC open image sets.