# `Color.RGB`

Linear (un-companded) RGB relative to a named working space.

See `Color.SRGB` for the companded sRGB working-space color type.
This module covers every RGB working space listed in
`Color.RGB.WorkingSpace`: `:SRGB`, `:Adobe`, `:ProPhoto`, `:Rec709`,
`:Rec2020` etc. Channels are unit floats.

The working-space conversion matrix is computed lazily and memoised
in `:persistent_term`, so the first call for a given working space
pays the Lindbloom derivation cost once and subsequent calls are a
plain `:persistent_term.get/1`.

# `t`

```elixir
@type t() :: %Color.RGB{
  alpha: Color.Types.alpha(),
  b: float() | nil,
  g: float() | nil,
  r: float() | nil,
  working_space: Color.Types.working_space() | nil
}
```

Linear RGB in any named working space. The `working_space` field
identifies which set of primaries and reference white to use; see
`Color.RGB.WorkingSpace.rgb_working_spaces/0` for the full list.

# `from_xyz`

Converts a CIE `XYZ` color to linear RGB in the given working space.

### Arguments

* `xyz` is a `Color.XYZ` struct. Its illuminant must match the working
  space — if not, chromatically adapt first.

* `working_space` is an atom naming the target RGB working space.

### Returns

* A `Color.RGB` struct.

### Examples

    iex> xyz = %Color.XYZ{x: 0.95047, y: 1.0, z: 1.08883, illuminant: :D65, observer_angle: 2}
    iex> {:ok, rgb} = Color.RGB.from_xyz(xyz, :SRGB)
    iex> {Float.round(rgb.r, 3), Float.round(rgb.g, 3), Float.round(rgb.b, 3)}
    {1.0, 1.0, 1.0}

# `to_xyz`

Converts a linear RGB color to CIE `XYZ`.

### Arguments

* `rgb` is a `Color.RGB` struct whose `:working_space` names an RGB
  working space (for example `:SRGB`, `:Adobe`, `:ProPhoto`).

### Returns

* A `Color.XYZ` struct tagged with the working space's illuminant
  and 2° observer angle.

### Examples

    iex> {:ok, xyz} = Color.RGB.to_xyz(%Color.RGB{r: 1.0, g: 1.0, b: 1.0, working_space: :SRGB})
    iex> {Float.round(xyz.x, 4), Float.round(xyz.y, 4)}
    {0.9505, 1.0}

---

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