@node Colors
@section Colors for Faces
-@cindex color name
-@cindex RGB triplet
Faces can have various foreground and background colors. When you
specify a color for a face---for instance, when customizing the face
(@pxref{Face Customization})---you can use either a @dfn{color name}
or an @dfn{RGB triplet}.
+@subsection Color Names
+@cindex color name
@findex list-colors-display
@vindex list-colors-sort
A color name is a pre-defined name, such as @samp{dark orange} or
text terminals; if a face is given a color specified by an X11 color
name, it is displayed using the closest-matching terminal color.
+@subsection RGB Triplets
+@cindex RGB triplet
An RGB triplet is a string of the form @samp{#RRGGBB}. Each of the
-R, G, and B components is a hexadecimal number specifying the
-component's relative intensity, one to four digits long (usually two
-digits are used). The components must have the same number of digits.
-For hexadecimal values A to F, either upper or lower case are
-acceptable.
+primary color components is represented by a hexadecimal number
+between @samp{00} (intensity 0) and @samp{FF} (the maximum intensity).
+It is also possible to use one, three, or four hex digits for each
+component, so @samp{red} can be represented as @samp{#F00},
+@samp{#fff000000}, or @samp{#ffff00000000}. The components must have
+the same number of digits. For hexadecimal values A to F, either
+upper or lower case are acceptable.
The @kbd{M-x list-colors-display} command also shows the equivalent
RGB triplet for each named color. For instance, @samp{medium sea
The result is a list of integer RGB values--(RED GREEN BLUE).
These values range from 0 to 65535; white is (65535 65535 65535).
-The returned value reflects the standard X definition of COLOR,
-regardless of whether the terminal can display it, so the return value
-should be the same regardless of what display is being used."
+The returned value reflects the standard Emacs definition of
+COLOR (see the info node `(emacs) Colors'), regardless of whether
+the terminal can display it, so the return value should be the
+same regardless of what display is being used."
(let ((len (length color)))
- (cond ((and (>= len 4) ;; X-style "#XXYYZZ" color spec
+ (cond ((and (>= len 4) ;; HTML/CSS/SVG-style "#XXYYZZ" color spec
(eq (aref color 0) ?#)
(member (aref color 1)
'(?0 ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9
- ?a ?b ?c ?d ?e ?f)))
- ;; Translate the string "#XXYYZZ" into a list
- ;; of numbers (XX YY ZZ). If the primary colors
- ;; are specified with less than 4 hex digits,
- ;; the used digits represent the most significant
- ;; bits of the value (e.g. #XYZ = #X000Y000Z000).
+ ?a ?b ?c ?d ?e ?f
+ ?A ?B ?C ?D ?E ?F)))
+ ;; Translate the string "#XXYYZZ" into a list of numbers
+ ;; (XX YY ZZ), scaling each to the {0..65535} range. This
+ ;; follows the HTML color convention, where both "#fff" and
+ ;; "#ffffff" represent the same color, white.
(let* ((ndig (/ (- len 1) 3))
+ (maxval (1- (ash 1 (* 4 ndig))))
(i1 1)
(i2 (+ i1 ndig))
- (i3 (+ i2 ndig)))
+ (i3 (+ i2 ndig))
+ (i4 (+ i3 ndig)))
(list
- (ash
- (string-to-number (substring color i1 i2) 16)
- (* 4 (- 4 ndig)))
- (ash
- (string-to-number (substring color i2 i3) 16)
- (* 4 (- 4 ndig)))
- (ash
- (string-to-number (substring color i3) 16)
- (* 4 (- 4 ndig))))))
- ((and (>= len 9) ;; X-style RGB:xx/yy/zz color spec
+ (/ (* (string-to-number
+ (substring color i1 i2) 16)
+ 65535)
+ maxval)
+ (/ (* (string-to-number
+ (substring color i2 i3) 16)
+ 65535)
+ maxval)
+ (/ (* (string-to-number
+ (substring color i3 i4) 16)
+ 65535)
+ maxval))))
+ ((and (>= len 9) ;; X-style rgb:xx/yy/zz color spec
(string= (substring color 0 4) "rgb:"))
- ;; Translate the string "RGB:XX/YY/ZZ" into a list
- ;; of numbers (XX YY ZZ). If fewer than 4 hex
- ;; digits are used, they represent the fraction
- ;; of the maximum value (RGB:X/Y/Z = #XXXXYYYYZZZZ).
+ ;; Translate the string "rgb:XX/YY/ZZ" into a list of
+ ;; numbers (XX YY ZZ), scaling each to the {0..65535}
+ ;; range. "rgb:F/F/F" is white.
(let* ((ndig (/ (- len 3) 3))
(maxval (1- (ash 1 (* 4 (- ndig 1)))))
(i1 4)
(i2 (+ i1 ndig))
- (i3 (+ i2 ndig)))
+ (i3 (+ i2 ndig))
+ (i4 (+ i3 ndig)))
(list
(/ (* (string-to-number
(substring color i1 (- i2 1)) 16)
- 255)
+ 65535)
maxval)
(/ (* (string-to-number
(substring color i2 (- i3 1)) 16)
- 255)
+ 65535)
maxval)
(/ (* (string-to-number
- (substring color i3) 16)
- 255)
+ (substring color i3 (1- i4)) 16)
+ 65535)
maxval))))
(t
(cdr (assoc color color-name-rgb-alist))))))
(defun tty-color-translate (color &optional frame)
"Given a color COLOR, return the index of the corresponding TTY color.
-COLOR must be a string that is either the color's name, or its X-style
-specification like \"#RRGGBB\" or \"RGB:rr/gg/bb\", where each primary.
-color can be given with 1 to 4 hex digits.
+COLOR must be a string that is either the color's name, or its
+color triplet specification like \"#RRGGBB\" or \"rgb:RR/GG/BB\",
+where each primary color can be given with 1 to 4 hex digits.
If COLOR is a color name that is found among supported colors in
`tty-color-alist', the associated index is returned. Otherwise, the
looking up the name in `color-name-rgb-alist', are used to find the
supported color that is the best approximation for COLOR in the RGB
space.
-If COLOR is neither a valid X RGB specification of the color, nor a
+If COLOR is neither a valid RGB specification of the color, nor a
name of a color in `color-name-rgb-alist', the returned value is nil.
If FRAME is unspecified or nil, it defaults to the selected frame."
x_query_colors (f, bgcolor, 1);
}
+#define HEX_COLOR_NAME_LENGTH 32
+
/* On frame F, translate the color name to RGB values. Use cached
information, if possible.
if (color_name[0] == '#')
{
- /* The hex form is parsed directly by XParseColor without
+ /* Don't pass #RGB strings directly to XParseColor, because that
+ follows the X convention of zero-extending each channel
+ value: #f00 means #f00000. We want the convention of scaling
+ channel values, so #f00 means #ff0000, just as it does for
+ HTML, SVG, and CSS.
+
+ So we translate #f00 to rgb:f/0/0, which X handles
+ differently. */
+ char rgb_color_name[HEX_COLOR_NAME_LENGTH];
+ int len = strlen (color_name);
+ int digits_per_channel;
+ if (len == 4)
+ digits_per_channel = 1;
+ else if (len == 7)
+ digits_per_channel = 2;
+ else if (len == 10)
+ digits_per_channel = 3;
+ else if (len == 13)
+ digits_per_channel = 4;
+ else
+ return 0;
+
+ snprintf (rgb_color_name, sizeof rgb_color_name, "rgb:%.*s/%.*s/%.*s",
+ digits_per_channel, color_name + 1,
+ digits_per_channel, color_name + digits_per_channel + 1,
+ digits_per_channel, color_name + 2 * digits_per_channel + 1);
+
+ /* The rgb form is parsed directly by XParseColor without
talking to the X server. No need for caching. */
- return XParseColor (dpy, cmap, color_name, color);
+ return XParseColor (dpy, cmap, rgb_color_name, color);
}
for (cache_entry = FRAME_DISPLAY_INFO (f)->color_names; cache_entry;
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