Mode for calculating the DotCode symbol size.
=-1: Default: The ratio between width and height is "3:2".
=0: Ratio Width/Height: The aspect ratio between columns and rows defines the size of the symbol.
Syntax: "<columns>:<rows>", e.g.: "2:1" for twice as much columns than rows.
=1: Fixed number of columns: The number of columns is fixed, the number of rows is calculated.
=2: Fixed number of rows: The number of rows is fixed, the number of columns is calculated.
=3: Fixed number of columns and rows: The number of columns and rows is fixed.