# Photo Histogram & Clipping Analyzer

> Inspect RGB histograms, clipped channels and tonal percentiles in a photo. Upload a photo to measure luminance and RGB distributions, shadow and highlight clipping, and tonal percentiles. Download the full 256-bin analysis and get percentile-based black and white starting points.

Part of usefulweb.site (https://usefulweb.site/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://luminahistogramanalyzer.usefulweb.site/ (interactive tool at https://luminahistogramanalyzer.usefulweb.site/tool)
- JSON API: POST https://luminahistogramanalyzer.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://luminahistogramanalyzer.usefulweb.site/api/v1/tool)
- OpenAPI: https://luminahistogramanalyzer.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://luminahistogramanalyzer.usefulweb.site/mcp - tool `lumina_histogram_analyzer`

## Inputs
- image (file, required): Image (PNG, JPEG or WebP; up to 8 MB and 16 MP)

## Method
- Auto-oriented, display-referred 8-bit sRGB analysis. Fully transparent pixels are excluded; other pixels count equally.
- Luma is rounded 0.2126 R + 0.7152 G + 0.0722 B. Clipping counts any channel at or below 2, or at or above 253. This does not measure sensor exposure or recover clipped RAW data.
- Report 1st, 50th and 99th luminance percentiles using nearest-rank selection. Suggested levels discard 0.5% from each luminance tail; flat or empty images retain 0–255. Values are suggestions, not an exposure judgment.