XSolarisGetVisualGamma(3Xmu) XLIB FUNCTIONS XSolarisGetVisualGamma(3Xmu)

NAME

XSolarisGetVisualGamma - obtain gamma information for a visual

SYNOPSIS

#include <X11/Xmu/XmuSolaris.h>

Status
XSolarisGetVisualGamma(Display *display, int screen_number,
Visual *visual, double *gamma);

ARGUMENTS

display Specifies the connection to the X server.

screen_number
Specifies the number of the screen.

visual Specifies the visual.

gamma Returns the gamma value for the specified visual.

DESCRIPTION

The XSolarisGetVisualGamma function returns the gamma value of a
specified visual. This value is the exponent of the power function
describing the intensity response of colors displayed using that
visual. This is the intensity response of the entire path from the
frame buffer pixel store through the monitor. The equation of the
intensity response is:

IntensityOut = (FramebufferColor)**gamma

(i.e. the color in the frame buffer raised to the power of gamma).

FramebufferColor refers to the the RGB values stored in the frame
buffer pixel store and processed by any color mapping LUTs that are
in the output path.

Gamma correction is necessary because of the way color intensities
are perceived by the human eye. Without gamma correction, the eye
interprets changes to the color intensity incorrectly. Small changes
to low intensity light appear to have more effect than the equivalent
change to higher intensity light. This distorts the appearance of
graphical entities which depend on accurate color, such as images,
anti-aliased lines and transparent polygons.

Gamma correction results in a linear mapping between color values and
perceived intensity. Gamma corrected visuals are also called linear
visuals for this reason. Linear visuals have a gamma value of 1.0.

Note: the term "gamma" used here refers the mapping applied along the
entire path (that is, the value perceived by the end user), not
merely the exponent of the gamma correction function.

The gamma value returned defines the color-to-intensity mapping for
all three channels: red, green, and blue.

A status of Success is returned if the function was able to determine
the gamma successfully. If a request failure occurred while calling
the function, a BadAccess error code is returned. If there is an
internal inconsistency (e.g. the gamma value for one of the color
channels is different from the others) a BadMatch error code is
returned. Whenever an error code is returned, the argument gamma is
left untouched.

The gamma value returned represents the best information available on
the intensity response of the visual. Depending on the device, it
may or may not include the actual monitor characteristics (some
devices have no way of determining the type of monitor so they may
assume a default monitor gamma). As such, it represents the system's
"best guess" about the intensity response. Since this function gets
its information from the same property used by Solaris color
management systems, if more accurate information on the monitor
response is configured or calibrated through these systems, this
function will return a more accurate value for gamma.

If the intensity mapping is not a power function, the returned gamma
value may only be approximate. This should usually happen only when
the device gamma correction has been incorrectly configured.

To use this function, an application should link with libXmu.

X Version 11 11 Jan 2008 XSolarisGetVisualGamma(3Xmu)