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Link: http://www.fltk.org/str.php?L2373
Version: 1.1.10


This is a suggestion for enhanced color documentation, 
chapter 3 - Common Widgets and Attributes

The text is ment to replace first part of Colors chapter. Be aware, that
links need to be added, when inserting to documentation.

Colors

FLTK manages colors as 32-bit unsigned integers. Values from 0 to 255
represent an index into the FLTK 1.0.x standard colormap and are allocated
as needed on screens without TrueColor support. The Fl_Color enumeration
type defines the standard colors and color cube for the first 256 colors.
All of these are named with symbols in <FL/Enumerations.H>.

Color values greater than 255 are treated as 24-bit RGB values. These are
mapped to the closest color supported by the screen, either from one of
the 256 colors in the FLTK 1.0.x colormap or a direct RGB value on
TrueColor screens.

In summary the 32-bit unsigned integer is encoded as RGBI, with a byte
each for R, G, B and I. When RGB bytes are non-zero, the value is treated
as RGB. If these bytes are zero the colormap will be used by index byte.

The function fl_rgb_color() generates Fl_Color out of specified 8-bit RGB
values or one 8-bit grayscale value.

For generating RGB values out of colormap index the class Fl provides two
methods Fl::get_color(). One generates RGB as single 8-bit values, the
other one encodes RGB as 32-bit unsigned integer. Also class Fl provides
methods Fl::get_system_colors(), Fl::foreground(), Fl::background()  and
Fl::background2() for setting system colors.

The standard colormap can be changed by using Fl::own_colormap(),
Fl::free_color() and Fl::set_color().

There are two predefined graphical interfaces for choosing colors. The
function fl_show_colormap() shows a table of colors and returns Fl_Color
value. The Fl_Color_Chooser widget provides a standard RGB color chooser.

Finally there are some functions for using colors in drawing:


Link: http://www.fltk.org/str.php?L2373
Version: 1.1.10

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