XQueryColor(XS)   X Version 11 (Release 5) 6 January 1993    XQueryColor(XS)


 Name

    XQueryColor - obtain color values

 Syntax


    XQueryColor(display, colormap, def_in_out)
          Display *display;
          Colormap colormap;
          XColor *def_in_out;

    XQueryColors(display, colormap, defs_in_out, ncolors)
          Display *display;
          Colormap colormap;
          XColor defs_in_out[];
          int ncolors;

    Status XLookupColor(display, colormap, color_name, exact_def_return,
                        screen_def_return)
          Display *display;
          Colormap colormap;
          char *color_name;
          XColor *exact_def_return, *screen_def_return;

    Status XParseColor(display, colormap, spec, exact_def_return)
          Display *display;
          Colormap colormap;
          char *spec;
          XColor *exact_def_return;


 Arguments


    colormap       Specifies the colormap.

    colorname     Specifies the color name string (for example, red) whose
                   color definition structure you want returned.

    definout     Specifies and returns the RGB values for the pixel speci-
                   fied in the structure.

    defsinout    Specifies and returns an array of color definition struc-
                   tures for the pixel specified in the structure.

    display        Specifies the connection to the X server.

    exactdefreturn
                   Returns the exact RGB values.

    ncolors        Specifies the number of XColor structures in the color
                   definition array.

    screendefreturn
                   Returns the closest RGB values provided by the hardware.

    spec           Specifies the color name string; case is ignored.

    exactdefreturn
                   Returns the exact color value for later use and sets the
                   DoRed, DoGreen, and DoBlue flags.

 Description

    The XQueryColor function returns the current RGB value for the pixel in
    the XColor structure and sets the DoRed, DoGreen, and DoBlue flags.  The
    XQueryColors function returns the RGB value for each pixel in each XColor
    structure, and sets the DoRed, DoGreen, and DoBlue flags in each struc-
    ture.

    XQueryColor and XQueryColors can generate ``BadColor'' and ``BadValue''
    errors.

    The XLookupColor 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 imple-
    mentation dependent.  Use of uppercase or lowercase does not matter.
    XLookupColor returns nonzero if the name is resolved, otherwise it
    returns zero.

    The XParseColor 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 Charac-
    ter Encoding the result is implementation dependent.  Use of uppercase or
    lowercase does not matter.  XParseColor returns nonzero if the name is
    resolved, otherwise it returns zero.

    XLookupColor and XParseColor can generate ``BadColor'' error.

 Color names

    An RGB Device specification is identified by the prefix ``rgb:'' and con-
    forms 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 follow-
    ing formats:

       #RGB           (4 bits each)
       #RRGGBB        (8 bits each)
       #RRRGGGBBB     (12 bits each)
       #RRRRGGGGBBBB  (16 bits each)


    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.

 Diagnostics


    ``BadColor''   A value for a Colormap argument does not name a defined
                   Colormap.

    ``BadValue''   Some numeric value falls outside the range of values
                   accepted by the request.  Unless a specific range is
                   specified for an argument, the full range defined by the
                   argument's type is accepted.  Any argument defined as a
                   set of alternatives can generate this error.

 See also

    XAllocColor(XS), XCreateColormap(XS), XStoreColors(XS)
    Xlib - C Language X Interface