/*
* Copyright (c) 2016 Metron, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Metron, Inc. nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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package com.metsci.glimpse.charts.shoreline.gshhs;
import java.io.BufferedInputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import com.metsci.glimpse.charts.shoreline.LandVertex;
import com.metsci.glimpse.charts.shoreline.gshhs.GshhsPolygonHeader.UnrecognizedValueException;
import com.metsci.glimpse.util.Pair;
import com.metsci.glimpse.util.io.LittleEndianDataInput;
import com.metsci.glimpse.util.io.StreamOpener;
/**
* The GSHHS dataset can be downloaded from ftp://ftp.soest.hawaii.edu/pwessel/gshhs/ .
*
* @author hogye
*/
public class GshhsReader
{
public static Pair<List<List<LandVertex>>, List<GshhsPolygonHeader>> readSegments( File file ) throws IOException
{
return readSegments( file.getPath( ), StreamOpener.file );
}
public static Pair<List<List<LandVertex>>, List<GshhsPolygonHeader>> readSegments( String location, StreamOpener streamOpener ) throws IOException
{
InputStream stream = null;
try
{
stream = streamOpener.openForRead( location );
return readSegments( stream );
}
finally
{
if ( stream != null ) try
{
stream.close( );
}
catch ( IOException e )
{
}
}
}
/**
* Closing the stream is left up to the caller.
*/
public static Pair<List<List<LandVertex>>, List<GshhsPolygonHeader>> readSegments( InputStream stream ) throws IOException
{
List<List<LandVertex>> segments = new ArrayList<List<LandVertex>>( );
List<GshhsPolygonHeader> headers = new ArrayList<GshhsPolygonHeader>( );
try
{
DataInputStream dataStream = new DataInputStream( new BufferedInputStream( stream ) );
DataInput in = ( isLittleEndian( dataStream ) ? new LittleEndianDataInput( dataStream ) : dataStream );
while ( true )
{
GshhsPolygonHeader header = new GshhsPolygonHeader( in );
// If the polygon crosses Greenwich, the header lists its westernmost lon
// as negative, but all its vertices still have lons between 0 and 360. We
// need to shift some vertices (those just west of Greenwich) by -360.
//
// If the polygon surrounds the north or south pole, we need to shift some
// vertices (those between 180 and 360) by -360. We also need to reorder
// the vertices so that those shifted by -360 come first. (Actually, this
// is a tough problem in general, since rebreaking the polygon at 180/-180
// could create new polygons. In practice, Antarctica is the only polygon
// we have to worry about, and rebreaking it is straightforward.)
//
// For any other polygon, we want to shift all the vertices by the same
// amount, so that the whole polygon is shifted together.
// North America, e.g.
boolean shiftWholePolygon = ( !header.crossesGreenwich && header.westLon_DEG >= 180 );
// Antarctica
boolean isAntarctica = ( header.southLat_DEG == -90 && header.westLon_DEG == 0 && header.eastLon_DEG == 360 );
List<LandVertex> segment = new ArrayList<LandVertex>( header.numVertices );
for ( int i = 0; i < header.numVertices; i++ )
{
// Longitude comes first.
double vertexLon_DEG = 1e-6 * in.readInt( );
double vertexLat_DEG = 1e-6 * in.readInt( );
// Western tip of Africa, e.g.
if ( header.crossesGreenwich && vertexLon_DEG >= 270 ) vertexLon_DEG -= 360;
// North America, e.g.
if ( shiftWholePolygon ) vertexLon_DEG -= 360;
// Antarctica
if ( isAntarctica && vertexLon_DEG >= 180 ) vertexLon_DEG -= 360;
segment.add( new LandVertex( vertexLat_DEG, vertexLon_DEG ) );
}
// Antarctica
if ( isAntarctica ) segment = rebreakAntarcticaSegment( segment );
segments.add( segment );
headers.add( header );
}
}
catch ( EOFException e )
{
return new Pair<List<List<LandVertex>>, List<GshhsPolygonHeader>>( segments, headers );
}
catch ( UnrecognizedValueException e )
{
throw new RuntimeException( e );
}
}
private static boolean isLittleEndian( DataInputStream stream ) throws IOException
{
stream.mark( 1024 );
try
{
new GshhsPolygonHeader( stream );
return false;
}
catch ( UnrecognizedValueException e )
{
}
finally
{
stream.reset( );
}
stream.mark( 1024 );
try
{
new GshhsPolygonHeader( new LittleEndianDataInput( stream ) );
return true;
}
catch ( UnrecognizedValueException e )
{
throw new RuntimeException( e );
}
finally
{
stream.reset( );
}
}
private static List<LandVertex> rebreakAntarcticaSegment( List<LandVertex> segment )
{
for ( int i = 0; i < segment.size( ); i++ )
{
LandVertex vertex = segment.get( i );
if ( vertex.lon > 0 )
{
List<LandVertex> newSegment = segment.subList( i, segment.size( ) );
newSegment.addAll( segment.subList( 0, i ) );
return newSegment;
}
}
throw new RuntimeException( "Failed to rebreak Antarctica segment" );
}
}