A color is used for specifying the additional visual distinction between
geometrical objects on the same layer or different layers, in the same block or
different blocks, or between objects independent of a layer or block. A color is
also used as a way to indicate lineweights for color-dependent plotting or to
display a visual property when it cannot be displayed another way. The
C++ platform supports various ways for working with a color and
transparency.
A color consists of using a 32-bit integer value in which the
various color components are packed. A color can be defined as a three-element
value that stores the red, green, and blue components; as an index of a palette
that stores the actual color value; as a reference to another object whose color
must be used, or as a foreground. Each definition way, named as a color
method, has its own features. The 32-bit packed integer value stores the color
method and color components that correspond together to the method.
A transparency consists
of using a 32-bit integer value in which the various transparency components
are packed. A transparency can be defined as an alpha value that is the degree
of clarity or as a reference to another object whose transparency must be
used. The 32-bit packed integer value stores the transparency method and
transparency components that correspond together to the method.
An alternative color definition is the naming of colors. The named
color is defined by a string that is the color name and a string that is stored in a
color book. The color book stores the set of
records that define how colors must be displayed. Color books can be saved as individual files from which they can be loaded in an application. Color books
provide individual settings of colors for specific devices or goals.
A color can also be defined as a database object that provides additional
functionality, such as the converting of color information in or from a .dwg or .dxf file, using named colors, and auditing color values.