The enlargement test corpus
Adjectives are cheap. This page is the evidence the other guides point to: a fixed set of test pictures, every method at every factor, and a fingerprint of each result that anyone can re-create in their own browser.
What is in it
6 synthetic pictures, each drawn by a few lines of code so that anyone gets exactly the same pixels. Each is enlarged by all four methods — Lanczos 3, Mitchell, Edge-guided, Nearest — at 2×, 3×, 4×, 8×, with no clean-up, no detail pass and no model: 102 fingerprints in all, counting the sources.
| Id | Size | What it tests |
|---|---|---|
| C06-logo-alpha | 60 × 24 | Transparent logo with an anti-aliased edge — transparency through every method, no dark fringe. |
| C07-pixel-art | 16 × 16 | Pixel-art sprite, 16 colours — nearest neighbour must add no colour. |
| C11-signature | 44 × 18 | Signature-like strokes on white — thin dark lines, the form-preset case. |
| C12-portrait | 30 × 38 | Portrait-style subject — a soft face-shaped blob on a plain background. |
| C19-gradient | 64 × 64 | Synthetic gradient — where tile seams and banding show first. |
| C20-steps | 32 × 32 | Synthetic step edges — ringing and the halo guard. |
A fingerprint is the SHA-256 of the picture’s raw RGBA bytes. Change one level of one channel of one pixel and it changes completely.
