Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

XQueryColor

HOME

XQueryColor

NAME
SYNTAX
ARGUMENTS
DESCRIPTION
COLOR NAMES
DIAGNOSTICS
SEE ALSO

NAME

XQueryColor, XQueryColors, XLookupColor, XParseColor − obtain color values

SYNTAX

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

ARGUMENTS


	colormap		Specifies the colormap.

color_name

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

def_in_out

Specifies and returns the RGB values for the pixel specified in the structure.

defs_in_out

Specifies and returns an array of color definition structures for the pixel specified in the structure.

display

Specifies the connection to the X server.

exact_def_return

Returns the exact RGB values.

ncolors

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

screen_def_return

Returns the closest RGB values provided by the hardware.

spec

Specifies the color name string; case is ignored.

exact_def_return

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 structure.

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 implementation-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 Character 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 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, the string ‘‘#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 plus or minus 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 plus or minus 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.

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.

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