Convert an LCH color to a Lab color

Turn chroma and hue degrees back into a and b.

JavaScript Version 1.0.0 · MIT · .md

function lchToLab([l, c, h]) { return [l, Math.cos((h * Math.PI) / 180) * c, Math.sin((h * Math.PI) / 180) * c]; }

Input & expected output

[
  50,
  10,
  0
]

[
  50,
  10,
  0
]

The edge case

[
  50,
  10,
  90
]

[
  50,
  6.123233995736766e-16,
  10
]

Know the limits

• Floating-point trigonometry leaves tiny residues such as 6e-16, as the edge case shows; round for display.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Convert Celsius to Fahrenheit — Apply the temperature conversion without rounding the result.
• Convert hex to RGB — Expand #rgb if needed and read the red, green and blue channels.
• Convert URL parameters to object — Read a query string into an object; repeated keys become arrays.