# `Color.Gamut.SVG`

Renders a chromaticity diagram — the horseshoe, gamut
triangles, Planckian locus, and optional palette / seed
overlays — as a self-contained SVG string.

The heavy lifting (spectral-locus points, working-space
triangle vertices, Planckian coordinates) is done by
`Color.Gamut.Diagram`; this module wraps that data in a
complete, styleable SVG.

Useful when you want to embed a chromaticity diagram in a
design-system docs page, a README, an exported PDF, or any
tool that speaks SVG. The same renderer is used by the
`/gamut` tab of `Color.Palette.Visualizer`.

## Example

    iex> svg = Color.Gamut.SVG.render(projection: :uv, gamuts: [:SRGB, :P3_D65])
    iex> String.starts_with?(svg, "<svg viewBox=")
    true

# `render`

```elixir
@spec render(keyword()) :: binary()
```

Renders the diagram as an SVG binary.

### Options

* `:projection` is `:uv` (default) or `:xy`.

* `:gamuts` is a list of working-space atoms to overlay as
  triangles. Default `[:SRGB, :P3_D65]`. Pass `[]` to render
  no triangles.

* `:planckian` — when `true` (default `false`), draws the
  Planckian locus from 1500 K to 20 000 K with annotation
  points at 2000, 2700, 4000, 6500, and 10 000 K.

* `:seed` — any `Color.input()`. When provided, a labelled
  dot is plotted at the colour's chromaticity.

* `:palette` — a `Color.Palette.Tonal` or
  `Color.Palette.ContrastScale` struct. When provided, every
  stop is plotted as a coloured circle with a `<title>` giving
  its label and hex. The seed stop is drawn slightly larger.

* `:width`, `:height` — SVG viewport dimensions. Defaults
  800 × 700. The inline CSS of the embedding page can scale
  this with `width: 100%`.

* `:gamut_colours` — a map of `working_space_atom => hex`
  overriding the default outline colour for specific spaces.

### Returns

* A binary containing a self-contained `<svg>…</svg>` element.

### Examples

    iex> svg = Color.Gamut.SVG.render(projection: :xy)
    iex> String.contains?(svg, "Chromaticity not shown directly") or String.contains?(svg, "polygon")
    true

    iex> palette = Color.Palette.Tonal.new("#3b82f6")
    iex> svg = Color.Gamut.SVG.render(palette: palette, seed: "#3b82f6")
    iex> String.contains?(svg, "<title>500:")
    true

---

*Consult [api-reference.md](api-reference.md) for complete listing*