thumbnail-legibility-checklisted

# Thumbnail Legibility Check Thumbnails are designed at 1280 pixels wide or larger and seen at about 168. Almost every bad thumbnail decision comes from judging it at the wrong size. This skill measures what actually survives, then puts the candidates through the conditions they will really face. ## When to use - Choosing between several thumbnail, cover, or preview-image candidates. - An image that looks strong at full size and disappears in a feed. - Checking whether on-image text or a face reads at small size. - Comparing a new candidate against what already performs. ## Step 1: measure ```bash python scripts/legibility.py path/to/candidates --recursive ``` Requires Pillow (`python -m pip install Pillow`). Add `--json` for machine output. Every candidate is cover-cropped and downscaled to 168x94, then measured: | Metric | What it means | Risk below or above | |---|---|---| | `bright` | Mean luminance | Under 45 sinks into a dark feed; over 200 washes out on white | | `contr` | Mean per-channel spread | Under 40 reads as flat at small size | | `pop` | Distance between strongest and weakest channel | Under 12 means muted, no colour signal in a feed | | `glance` | Contrast surviving a heavy blur | Low means it turns to mush during a fast scroll | | `gray` | Contrast with colour removed | Low means the design leans on hue alone for separation | These are risk signals, not verdicts. A dark thumbnail can be the right choice when the channel's whole look is dark. Use the