# Photo Palette & Text Contrast

> Check palette luminance and choose readable text for photos and graphics. Analyze up to 64 six-digit hex colors for relative luminance and contrast against black and white. Use the results to choose watermark or caption colors for opaque backgrounds.

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://luminacoloranalyzer.usefulweb.site/ (interactive tool at https://luminacoloranalyzer.usefulweb.site/tool)
- JSON API: POST https://luminacoloranalyzer.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://luminacoloranalyzer.usefulweb.site/api/v1/tool)
- OpenAPI: https://luminacoloranalyzer.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://luminacoloranalyzer.usefulweb.site/mcp - tool `lumina_color_analyzer`

## Inputs
- colors (textarea): Hex colors (comma or space separated)

## Method
- Convert sRGB components to linear light and calculate relative luminance using coefficients 0.2126, 0.7152 and 0.0722.
- Contrast ratio is (lighter luminance + 0.05) / (darker luminance + 0.05). Choose black or white by the larger ratio.
- A single color cannot certify text over an entire photograph. Check the actual text area and opacity.