/// <summary>
/// Reads the header of a Shapefile
/// </summary>
/// <param name="reader">The Shapefile stream</param>
/// <returns>The shapefile header</returns>
private void ReadFileHeader(BinaryReader reader, out ShapefileShapeType shapeType, out BoundingBox bounds)
{
// Read File Code.
int FileCode = NumberReader.ReadIntBE(reader);
//Verify that the file has the correct file code (9994)
if (FileCode != 9994)
{
throw new FormatException("Invalid FileCode encountered. Expecting a file code of 9994.");
}
//Skip unused section
reader.BaseStream.Seek(20, SeekOrigin.Current);
// Read the File Length.
long fileLength = NumberReader.ReadIntBE(reader);
// Skip the Version number of the shapefile.
reader.BaseStream.Seek(4, SeekOrigin.Current);
// Get the shape type of the shapefile. Note that shapefiles can only contain one type of shape per file
shapeType = (ShapefileShapeType)NumberReader.ReadIntLE(reader);
// Get the bounding box of the Bounding Box.
bounds = ReadBoundingBox(reader);
}
/// <summary>
/// Reads LineString shapefile
/// </summary>
/// <param name="reader">The shapefile stream</param>
/// <returns>A list of Geometry objects</returns>
private async Task <List <Geometry> > ReadLineStringData(BinaryReader reader)
{
var items = new List <Geometry>();
int numParts, numPoints;
while (reader.BaseStream.Position < reader.BaseStream.Length)
{
Geometry item;
// Read Record Header.
int id = ReadRecordHeader(reader);
var boundingBox = ReadBoundingBox(reader);
// Read the number of Parts and Points in the shape.
numParts = NumberReader.ReadIntLE(reader);
numPoints = NumberReader.ReadIntLE(reader);
int[] parts = ReadParts(reader, numParts, numPoints);
//First read all the rings
var rings = new List <CoordinateCollection>();
var multiline = new MultiLineString();
for (int ringID = 0; ringID < numParts; ringID++)
{
var line = new LineString();
for (int i = parts[ringID]; i < parts[ringID + 1]; i++)
{
line.Vertices.Add(ReadCoordinate(reader));
}
if (optimize)
{
line.Vertices = await SpatialTools.VertexReductionAsync(line.Vertices, tolerance);
}
multiline.Geometries.Add(line);
}
if (numParts == 1)
{
item = (Geometry)multiline.Geometries[0];
}
else
{
item = multiline;
}
item.Metadata.ID = id.ToString();
item.Metadata.Properties.Add("BoundingBox", boundingBox);
items.Add(item);
}
return(items);
}
/// <summary>
/// Read the Parts index array for a record
/// </summary>
/// <param name="reader">The Shapefile stream</param>
/// <param name="numParts">The number of parts in the array</param>
/// <param name="numPoints">The number of points in total</param>
/// <returns>An array of part indexes</returns>
private int[] ReadParts(BinaryReader reader, int numParts, int numPoints)
{
int[] parts = new int[numParts + 1];
for (int i = 0; i < numParts; i++)
{
parts[i] = NumberReader.ReadIntLE(reader);
}
parts[numParts] = numPoints;
return(parts);
}
/// <summary>
/// Reads MultiPoint shapefile
/// </summary>
/// <param name="reader">The Shapefile stream</param>
/// <returns>A list of Geometry objects</returns>
private List <Geometry> ReadMultiPointData(BinaryReader reader)
{
var items = new List <Geometry>();
int numPoints;
// For each header
while (reader.BaseStream.Position < reader.BaseStream.Length)
{
Geometry item;
// Read Record Header.
int id = ReadRecordHeader(reader);
var boundingBox = ReadBoundingBox(reader);
// Num Points.
numPoints = NumberReader.ReadIntLE(reader);
if (numPoints == 1) //if there is only one point then create a point geography
{
item = new Point(ReadCoordinate(reader));
}
else
{
MultiPoint mp = new MultiPoint(numPoints);
// Read in all the Points.
for (int i = 0; i < numPoints; i++)
{
mp.Geometries.Add(new Point(ReadCoordinate(reader)));
}
item = mp;
}
item.Metadata.ID = id.ToString();
item.Metadata.Properties.Add("Bounding Box", boundingBox);
items.Add(item);
}
return(items);
}
/// <summary>
/// Read a shapefile Polygon record.
/// </summary>
/// <param name="reader">The Shapefile stream</param>
/// <returns>A list of Geometry objects</returns>
private List <Geometry> ReadPolygonData(BinaryReader reader)
{
var items = new List <Geometry>();
int numParts, numPoints;
while (reader.BaseStream.Position < reader.BaseStream.Length)
{
Geometry item;
// Read Record Header.
int id = ReadRecordHeader(reader);
var boundingBox = ReadBoundingBox(reader);
// Read the number of Parts and Points in the shape.
numParts = NumberReader.ReadIntLE(reader);
numPoints = NumberReader.ReadIntLE(reader);
int[] parts = ReadParts(reader, numParts, numPoints);
//First read all the rings
var rings = new List <CoordinateCollection>();
for (int ringID = 0; ringID < numParts; ringID++)
{
var ring = new CoordinateCollection();
for (int i = parts[ringID]; i < parts[ringID + 1]; i++)
{
ring.Add(ReadCoordinate(reader));
}
if (optimize)
{
ring = SpatialTools.VertexReduction(ring, tolerance);
}
rings.Add(ring);
}
// Vertices for a single, ringed polygon are always in clockwise order.
// Rings defining holes in these polygons have a counterclockwise orientation.
bool[] IsCounterClockWise = new bool[rings.Count];
int PolygonCount = 0;
//determine the orientation of each ring.
for (int i = 0; i < rings.Count; i++)
{
IsCounterClockWise[i] = rings[i].IsCCW();
if (!IsCounterClockWise[i])
{
PolygonCount++; //count the number of polygons
}
}
//if the polygon count is 1 then there is only one polygon to create.
if (PolygonCount == 1)
{
Polygon polygon = new Polygon();
polygon.ExteriorRing = rings[0];
if (rings.Count > 1)
{
for (int i = 1; i < rings.Count; i++)
{
polygon.InteriorRings.Add(rings[i]);
}
}
item = polygon;
}
else
{
MultiPolygon multPolygon = new MultiPolygon();
Polygon poly = new Polygon();
poly.ExteriorRing = rings[0];
for (int i = 1; i < rings.Count; i++)
{
if (!IsCounterClockWise[i])
{
multPolygon.Geometries.Add(poly);
poly = new Polygon(rings[i]);
}
else
{
poly.InteriorRings.Add(rings[i]);
}
}
multPolygon.Geometries.Add(poly);
item = multPolygon;
}
item.Metadata.ID = id.ToString();
item.Metadata.Properties.Add("Bounding Box", boundingBox);
items.Add(item);
}
return(items);
}
