XQueryColor(), XQueryColors(), XLookupColor(), XParseColor() - obtain color values
XQueryColor (Display *display, Colormap colormap,
XColor *def_in_out)
XQueryColors (Display *display, Colormap colormap,
XColor defs_in_out[], int ncolors)
Status XLookupColor (Display *display, Colormap colormap,
char *color_name, XColor *exact_def_return,
XColor *screen_def_return)
Status XParseColor (Display *display, Colormap colormap,
char *spec, XColor *exact_def_return)
The XQueryColor(3) function returns the current RGB value for the pixel in the XColor structure and sets the DoRed, DoGreen, and DoBlue flags. The XQueryColors(3) function returns the RGB value for each pixel in each XColor structure, and sets the DoRed, DoGreen, and DoBlue flags in each structure.
XQueryColor(3) and XQueryColors(3) can generate BadColor and BadValue errors.
The XLookupColor(3) function looks up the string name of a color with respect to the screen associated with the specified colormap. It returns both the exact color values and the closest values provided by the screen with respect to the visual type of the specified colormap. If the color name is not in the Host Portable Character Encoding the result is implementation dependent. Use of uppercase or lowercase does not matter. XLookupColor(3) returns nonzero if the name is resolved, otherwise it returns zero.
The XParseColor(3) function looks up the string name of a color with respect to the screen associated with the specified colormap. It returns the exact color value. If the color name is not in the Host Portable Character Encoding the result is implementation dependent. Use of uppercase or lowercase does not matter. XParseColor(3) returns nonzero if the name is resolved, otherwise it returns zero.
XLookupColor(3) and XParseColor(3) can generate BadColor error.
An RGB Device specification is identified by the prefix "rgb:" and conforms to the following syntax:
rgb:<red>/<green>/<blue>
<red>, <green>, <blue> := h | hh | hhh | hhhh
h := single hexadecimal digits (case insignificant)
Note that h indicates the value scaled in 4 bits, hh the value scaled in 8 bits, hhh the value scaled in 12 bits, and hhhh the value scaled in 16 bits, respectively.
For backward compatibility, an older syntax for RGB Device is supported, but its continued use is not encouraged. The syntax is an initial sharp sign character followed by a numeric specification, in one of the following formats:
The R, G, and B represent single hexadecimal digits. When fewer than 16 bits each are specified, they represent the most-significant bits of the value (unlike the "rgb:" syntax, in which values are scaled). For example, #3a7 is the same as #3000a0007000.
An RGB intensity specification is identified by the prefix "rgbi:" and conforms to the following syntax:
rgbi:<red>/<green>/<blue>
Note that red, green, and blue are floating point values between 0.0 and 1.0, inclusive. The input format for these values is an optional sign, a string of numbers possibly containing a decimal point, and an optional exponent field containing an E or e followed by a possibly signed integer string.
The standard device-independent string specifications have the following syntax:
CIEXYZ:<X>/<Y>/<Z>
CIEuvY:<u>/<v>/<Y>
CIExyY:<x>/<y>/<Y>
CIELab:<L>/<a>/<b>
CIELuv:<L>/<u>/<v>
TekHVC:<H>/<V>/<C>
All of the values (C, H, V, X, Y, Z, a, b, u, v, y, x) are floating point values. The syntax for these values is an optional '+' or '-' sign, a string of digits possibly containing a decimal point, and an optional exponent field consisting of an 'E' or 'e' followed by an optional '+' or '-' followed by a string of digits.
Xlib