Convert a Lab color to an LCH color

Turn a and b into chroma and hue degrees.

JavaScript Version 1.0.0 · MIT · .md

function labToLch([l, a, b]) { return [l, Math.hypot(a, b), ((Math.atan2(b, a) * 180) / Math.PI + 360) % 360]; }

Input & expected output

[
  52,
  40,
  30
]

[
  52,
  50,
  36.86989764584405
]

The edge case

[
  50,
  0,
  -10
]

[
  50,
  10,
  270
]

Know the limits

• Hue is normalized to 0–360°; the original could return negative hues, as the edge case would.
• Assumes CIE Lab input; it does not convert from sRGB.

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.