Function: read-color

read-color is an interactive and byte-compiled function defined in faces.el.gz.

Signature

(read-color &optional PROMPT CONVERT-TO-RGB ALLOW-EMPTY-NAME MSG FOREGROUND)

Documentation

Read a color name or RGB triplet.

Completion is available for color names, but not for RGB triplets.

RGB triplets have the form "#RRGGBB". Each of the R, G, and B components can have one to four digits, but all three components must have the same number of digits. Each digit is a hex value between 0 and F; either upper case or lower case for A through F are acceptable.

In addition to standard color names and RGB hex values, the following are available as color candidates. In each case, the corresponding color is used.

 * foreground at point - foreground under the cursor
 * background at point - background under the cursor

Optional arg PROMPT is the prompt; if nil, use a default prompt.

Interactively, or with optional arg CONVERT-TO-RGB-P non-nil, convert an input color name to an RGB hex string. Return the RGB hex string.

If optional arg ALLOW-EMPTY-NAME is non-nil, the user is allowed to enter an empty color name (the empty string).

Interactively, or with optional arg MSG non-nil, print the resulting color name in the echo area.

Interactively, displays a list of colored completions. If optional argument FOREGROUND is non-nil, shows them as foregrounds, otherwise as backgrounds.

View in manual

Probably introduced at or before Emacs version 23.1.

Key Bindings

Aliases

facemenu-read-color

Source Code

;; Defined in /usr/src/emacs/lisp/faces.el.gz
(defun read-color (&optional prompt convert-to-RGB allow-empty-name msg
			     foreground)
  "Read a color name or RGB triplet.
Completion is available for color names, but not for RGB triplets.

RGB triplets have the form \"#RRGGBB\".  Each of the R, G, and B
components can have one to four digits, but all three components
must have the same number of digits.  Each digit is a hex value
between 0 and F; either upper case or lower case for A through F
are acceptable.

In addition to standard color names and RGB hex values, the
following are available as color candidates.  In each case, the
corresponding color is used.

 * `foreground at point'   - foreground under the cursor
 * `background at point'   - background under the cursor

Optional arg PROMPT is the prompt; if nil, use a default prompt.

Interactively, or with optional arg CONVERT-TO-RGB-P non-nil,
convert an input color name to an RGB hex string.  Return the RGB
hex string.

If optional arg ALLOW-EMPTY-NAME is non-nil, the user is allowed
to enter an empty color name (the empty string).

Interactively, or with optional arg MSG non-nil, print the
resulting color name in the echo area.

Interactively, displays a list of colored completions.  If optional
argument FOREGROUND is non-nil, shows them as foregrounds, otherwise
as backgrounds."
  (interactive "i\np\ni\np")    ; Always convert to RGB interactively.
  (let* ((completion-ignore-case t)
	 (colors (append '("foreground at point" "background at point")
			 (if allow-empty-name '(""))
                         (if (display-color-p)
                             (defined-colors-with-face-attributes
                               nil foreground)
                           (defined-colors))))
	 (color (completing-read
		 (or prompt "Color (name or #RGB triplet): ")
		 ;; Completing function for reading colors, accepting
		 ;; both color names and RGB triplets.
		 (lambda (string pred flag)
		   (cond
		    ((null flag)        ; Try completion.
		     (or (try-completion string colors pred)
			 (if (color-defined-p string)
			     string)))
		    ((eq flag t)        ; List all completions.
		     (or (all-completions string colors pred)
			 (if (color-defined-p string)
			     (list string))))
		    ((eq flag 'lambda)  ; Test completion.
		     (or (member string colors)
			 (color-defined-p string)))))
		 nil t)))

    ;; Process named colors.
    (when (member color colors)
      (cond ((string-equal color "foreground at point")
	     (setq color (foreground-color-at-point)))
	    ((string-equal color "background at point")
	     (setq color (background-color-at-point))))
      (when (and convert-to-RGB
		 (not (string-equal color "")))
        (let ((components (color-values color)))
	  (unless (string-match-p "^#\\(?:[[:xdigit:]][[:xdigit:]][[:xdigit:]]\\)+$" color)
	    (setq color (format "#%04X%04X%04X"
				(logand 65535 (nth 0 components))
				(logand 65535 (nth 1 components))
				(logand 65535 (nth 2 components))))))))
    (when msg (message "Color: `%s'" color))
    color))