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NetTopologySuite.IO.TinyWKB

An IO module for NTS to read and write geometries in the Tiny Well-Known-Binary format.

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Usage

Reading

Read a geometry like this. A TinyWkbReader is reusable.

/*
 bytes ... Array of bytes (byte[]) with twkb data from somewhere.
           You can also pass a Stream or a BinaryReader
 */
var geometryReader = new TinyWkbReader();
var geometry = geometryReader.Read(bytes);

Reading id-lists

For MULTI-geometries or GEOMETRYCOLLECTIONs the TWKB specification supports storing an identifier (System.Int64) for each contained geometry. There are 3 possible ways to obtain or handle these:

The identifier is stored in the Geometry.UserData object (default).
The caller subscribes to the TinyWkbReader.IdentifiersProvided event.
The event's arguments provide access to the geometry that has been read along with the list of identifiers.
Call the TinyWkbReader.Read(byte[], out IList<long> idList) overload.

var geometryReader = new TinyWkbReader();
var geometry = geometryReader.Read(bytes, out var idList);

Writing

Write geometries like this. A TinyWkbWriter is reusable.

/*
 Create the writer. All constructor arguments are optional, the
 default values are displayed.
 */
var geometryWriter = new TinyWkbWriter(
    precisionXY: 7,    // Number of decimal places for x- and y-ordinate values.
    emitZ: true,       // Emit z-ordinate values if geometry has them
    precisionZ: 7,     // number of decimal digits for z-ordinates
    emitM: true,       // Emit m-ordinate values if geometry has them
    precisionM: 7,     // number of decimal digits for m-ordinates
    emitSize: false,   // Emit the size of the geometry definition 
    emitBoundingBox: true, 
                       // Emit the bounding box of the geometry for all dimensions 
    emitIdList: false  // Emit a list of identifiers, one for every geometry in a
                       //   MULTI-geometry or GEOMETRYCOLLECTION
);

/*
 geometry ... Geometry from somewhere.

 There are overloads for Write that take a Stream or
 BinaryWriter as argument.
 */
var bytes = geometryWriter.Write(geometry);

Writing id-lists

As noted in [Reading id-lists] TWKB has the concept of identifiers for MULTI-geometries or GEOMETRYCOLLECTIONs. Writing identifiers is supported analogous to the reading mechanism:

The identifier is taken from Geometry.UserData. If that does not work, a new System.Int64 value is created and used.
The caller subscribes to the TinyWkbWriter.IdentifiersRequested event, and fills adds the identifiers to the event's arguments.
Call one of the TinyWkbWriter.Write overloads that takes an IList<System.Int64> idList argument.

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