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Fix color component calculations in color.el

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* lisp/color.el (color-name-to-rgb): Use 16 bits per color component.
(color-rgb-to-hex): Accept an optional argument
DIGITS-PER-COMPONENT, defaulting to 4, and format the hexadecimal
notation either for 8 or 16 bits per component.  (Bug#25890)
* lisp/net/shr-color.el (shr-color->hexadecimal): Call
color-rgb-to-hex with the optional argument of 2, to match color
processing on the Web.
This commit is contained in:
Eli Zaretskii 2017-03-03 16:05:02 +02:00
parent 244de7b0ed
commit 7b00e956b4
2 changed files with 11 additions and 7 deletions
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16
lisp/color.el
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@ -52,14 +52,18 @@ displayed. If FRAME is omitted or nil, use the selected frame.
If FRAME cannot display COLOR, return nil."
;; `colors-values' maximum value is either 65535 or 65280 depending on the
;; display system. So we use a white conversion to get the max value.
(let ((valmax (float (car (color-values "#ffffff")))))
(let ((valmax (float (car (color-values "#ffffffffffff")))))
(mapcar (lambda (x) (/ x valmax)) (color-values color frame))))
(defun color-rgb-to-hex (red green blue)
"Return hexadecimal notation for the color RED GREEN BLUE.
RED, GREEN, and BLUE should be numbers between 0.0 and 1.0, inclusive."
(format "#%02x%02x%02x"
(* red 255) (* green 255) (* blue 255)))
(defun color-rgb-to-hex (red green blue &optional digits-per-component)
"Return hexadecimal #RGB notation for the color specified by RED GREEN BLUE.
RED, GREEN, and BLUE should be numbers between 0.0 and 1.0, inclusive.
Optional argument DIGITS-PER-COMPONENT can be either 4 (the default)
or 2; use the latter if you need a 24-bit specification of a color."
(or digits-per-component (setq digits-per-component 4))
(let* ((maxval (if (= digits-per-component 2) 255 65535))
(fmt (if (= digits-per-component 2) "#%02x%02x%02x" "#%04x%04x%04x")))
(format fmt (* red maxval) (* green maxval) (* blue maxval))))
(defun color-complement (color-name)
"Return the color that is the complement of COLOR-NAME.

2
lisp/net/shr-color.el
View File

@ -260,7 +260,7 @@ Like rgb() or hsl()."
(l (/ (string-to-number (match-string-no-properties 3 color)) 100.0)))
(destructuring-bind (r g b)
(shr-color-hsl-to-rgb-fractions h s l)
(color-rgb-to-hex r g b))))
(color-rgb-to-hex r g b 2))))
;; Color names
((cdr (assoc-string color shr-color-html-colors-alist t)))
;; Unrecognized color :(