Function: erc-nicks--get-luminance

erc-nicks--get-luminance is a byte-compiled function defined in erc-nicks.el.gz.

Signature

(erc-nicks--get-luminance COLOR)

Documentation

Return relative luminance of COLOR.

COLOR can be a list of normalized values or a name. This is the same as the Y component returned by color-srgb-to-xyz.

Source Code

;; Defined in /usr/src/emacs/lisp/erc/erc-nicks.el.gz
;; https://stackoverflow.com/questions/596216#answer-56678483
(defun erc-nicks--get-luminance (color)
  "Return relative luminance of COLOR.
COLOR can be a list of normalized values or a name.  This is the
same as the Y component returned by `color-srgb-to-xyz'."
  (let ((out 0)
        (coefficients '(0.2126 0.7152 0.0722))
        (chnls (if (stringp color) (color-name-to-rgb color) color)))
    (dolist (ch chnls out)
      (cl-incf out (* (pop coefficients)
                      (if (<= ch 0.04045)
                          (/ ch 12.92)
                        (expt (/ (+ ch 0.055) 1.055) 2.4)))))))