Grapher imports and exports Golden Software Blanking Files .BLN.
Golden Software Blanking File .BLN is an ASCII format file used to store geographic information including areas, curves, and points. Spatial information is only concerned with the location of objects in space (i.e., their coordinates) and not with their attributes (i.e. line or fill style, marker symbol used, text labels, etc.). Even though the primary use of GS Blanking files is to indicate regions to be "blanked-out", they can also be used for simple boundaries and decorative illustrations.
The general format of the file is:
length,flag "Pname 1"
length,flag "Pname 2"
The length value is an integer which indicates the number of X, Y coordinate pairs that follow.
The flag value is 1 if the region inside areas is to be blanked and 0 if the region outside areas is to be blanked.
Pname is optional and is the name of a primary ID to be associated with the object. The primary ID is used to link the object to external data.
X, Y Coordinates
Following lines contain the actual X, Y coordinate pairs that make up the object. These can be integers or real numbers, and are stored 1 pair per line.
Type of Object
The type of object is determined as follows:
If the type/length field is 1, the object is considered a point. One coordinate pair follows.
If the type/length field is greater than 1 and the first and last coordinate pairs are equal, the object is considered a simple closed area. Otherwise, the object is considered a curve.
This example shows a simple .BLN file, with a single area:
This example shows a complex .BLN file, with an island:
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