Color.CAM16UCS (Color v0.4.0)

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CAM16-UCS perceptual color space.

CAM16 is a full color appearance model (Li et al. 2017, an update of CIECAM02). CAM16-UCS is its uniform-color-space projection — a (J', a', b') triple where equal Euclidean distance corresponds to equal perceptual difference, even better than CIELAB.

Conversions assume standard default viewing conditions:

  • Reference white: D65.

  • Adapting luminance L_A = 64 / π / 5 ≈ 4.074 cd/m².

  • Background relative luminance Y_b = 20.

  • Average surround (F = 1.0, c = 0.69, N_c = 1.0).

If you need non-default viewing conditions you can pass them as options.

Summary

Types

t()

A Color.CAM16UCS colour. The CAM16-UCS uniform space coordinates: j is lightness in [0, 100], a and b are red-green and yellow-blue chromatic coordinates.

Functions

from_xyz(xyz, options \\ [])

Converts CIE XYZ (D65, Y ∈ [0, 1]) to CAM16-UCS.

to_xyz(cam16_ucs, options \\ [])

Converts CAM16-UCS to CIE XYZ (D65, Y ∈ [0, 1]).

Types

t()

@type t() :: %Color.CAM16UCS{
  a: float() | nil,
  alpha: Color.Types.alpha(),
  b: float() | nil,
  j: float() | nil
}

A Color.CAM16UCS colour. The CAM16-UCS uniform space coordinates: j is lightness in [0, 100], a and b are red-green and yellow-blue chromatic coordinates.

Functions

from_xyz(xyz, options \\ [])

Converts CIE XYZ (D65, Y ∈ [0, 1]) to CAM16-UCS.

Arguments

  • xyz is a Color.XYZ struct.

  • options is a keyword list.

Options

  • :viewing_conditions is a map with :xyz_w, :la, :yb, and :surround. Defaults to D65 / L_A = 4.074 / Y_b = 20 / average.

Returns

Examples

iex> {:ok, ucs} = Color.CAM16UCS.from_xyz(%Color.XYZ{x: 0.95047, y: 1.0, z: 1.08883, illuminant: :D65, observer_angle: 2})
iex> {Float.round(ucs.j, 2), :math.sqrt(ucs.a * ucs.a + ucs.b * ucs.b) < 3.0}
{100.0, true}

to_xyz(cam16_ucs, options \\ [])

Converts CAM16-UCS to CIE XYZ (D65, Y ∈ [0, 1]).

Arguments

Returns