Ground reference: the same text, six grounds, four fills
What is behind the words decides the result more than anything else. Here the same line — “SALE 24” in white — is drawn over six grounds and cleared by each of this site’s four instant fills, with the letters-only mask. Because each ground existed before the lettering was drawn, every result can be measured against the truth: the number under each picture is how far the rebuilt pixels sit from the hidden ground, in colour levels out of 255.
Marked Visible when the mean is above 6 levels or the site’s own after-run check flags the region. Grain and foliage carry noise of their own, so a few levels there is the noise, not the fill.
Flat colour
A poster panel or an interface background.
Before 
Flat colour · 0 levels 
Gradient fit · 0 levels · linear ramp 
Diffusion · 0 levels 
Patch · 0 levels
Linear gradient
A slide or banner fading across.
Before 
Flat colour · 8.9 levelsVisible 
Gradient fit · 0 levels · linear ramp 
Diffusion · 0.7 levels 
Patch · 0.1 levels
Radial glow
A spotlight or vignette behind a headline.
Before 
Flat colour · 13.9 levelsVisible 
Gradient fit · 2.8 levels · radial ramp 
Diffusion · 1.4 levels 
Patch · 5.2 levels
Paper grain
A scan or a photo of a page: even, with noise.
Before 
Flat colour · 4 levels 
Gradient fit · 4 levels · linear ramp 
Diffusion · 4.7 levels 
Patch · 5.1 levels
Brick lines
Mortar lines crossing behind the words — structure no instant fill can invent.
Before 
Flat colour · 29.5 levelsVisible 
Gradient fit · 33.7 levels · linear rampVisible 
Diffusion · 31.5 levelsVisible 
Patch · 37.3 levelsVisible
Foliage
Leaves and grass: busy texture with no repeat.
Before 
Flat colour · 10.6 levelsVisible 
Gradient fit · 8.1 levels · linear rampVisible 
Diffusion · 5.7 levels 
Patch · 14.7 levelsVisible
All the numbers
| Ground | Flat colour | Gradient fit | Diffusion | Patch |
|---|---|---|---|---|
| Flat colour | 0 | 0 | 0 | 0 |
| Linear gradient | 8.9 · visible | 0 | 0.7 | 0.1 |
| Radial glow | 13.9 · visible | 2.8 | 1.4 | 5.2 |
| Paper grain | 4 | 4 | 4.7 | 5.1 |
| Brick lines | 29.5 · visible | 33.7 · visible | 31.5 · visible | 37.3 · visible |
| Foliage | 10.6 · visible | 8.1 · visible | 5.7 | 14.7 · visible |
Flat colour is exact on a flat panel and nowhere else. Gradient fit follows straight and curved fades. Diffusion is the quiet all-rounder on soft grounds. Patch keeps grain but can copy the wrong thing on foliage. Nothing instant rebuilds brick lines that cross the words — the structure was never visible to the fill.
How these are made
Every picture and number on this page is produced by one script running this site’s own fill engine — the same code the tool runs in your browser — on grounds drawn from a fixed seed, so running it again gives the same files unless the engine changes: node --import ./tests/unit/ts-resolve.mjs scripts/make-ground-reference.mjs. The lettering is a 5 × 7 block font scaled four times; the region box is 176 × 40 pixels; padding 2, feather 1.
The structure-aware model is not on this page: it runs only in the browser, through its runtime, and its answers on crossing structure are plausible inventions rather than measurements worth tabulating. Try it on your own picture in the main tool.
Ground Reference · before and after, cleared by this site's own engine