AutoCAD Color Index (ACI)¶

The color attribute represents an ACI (AutoCAD Color Index). AutoCAD and many other CAD application provides a default color table, but pen table would be the more correct term. Each ACI entry defines the color value, the line weight and some other attributes to use for the pen. This pen table can be edited by the user or loaded from an CTB or STB file. ezdxf provides functions to create (new()) or modify (ezdxf.acadctb.load()) plot styles files.

DXF R12 and prior are not good in preserving the layout of a drawing, because of the lack of a standard color table defined by the DXF reference and missing DXF structures to define these color tables in the DXF file. So if a CAD user redefined an ACI and do not provide a CTB or STB file, you have no ability to determine which color or lineweight was used. This is better in later DXF versions by providing additional DXF attributes like lineweight and true_color.