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LASwriteItemCompressed_GPSTIME11_v2.cs
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LASwriteItemCompressed_GPSTIME11_v2.cs
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//===============================================================================
//
// FILE: laswriteitemcompressed_gpstime11_v2.cs
//
// CONTENTS:
//
// Implementation of LASwriteItemCompressed for GPSTIME11 items (version 2).
//
// PROGRAMMERS:
//
// martin.isenburg@rapidlasso.com - http://rapidlasso.com
//
// COPYRIGHT:
//
// (c) 2005-2012, martin isenburg, rapidlasso - tools to catch reality
// (c) of the C# port 2014 by Shinta <shintadono@googlemail.com>
//
// This is free software; you can redistribute and/or modify it under the
// terms of the GNU Lesser General Licence as published by the Free Software
// Foundation. See the COPYING file for more information.
//
// This software is distributed WITHOUT ANY WARRANTY and without even the
// implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
//
// CHANGE HISTORY: omitted for easier Copy&Paste (pls see the original)
//
//===============================================================================
using System.Diagnostics;
namespace laszip.net
{
class LASwriteItemCompressed_GPSTIME11_v2 : LASwriteItemCompressed
{
const int LASZIP_GPSTIME_MULTI=500;
const int LASZIP_GPSTIME_MULTI_MINUS=-10;
const int LASZIP_GPSTIME_MULTI_UNCHANGED=(LASZIP_GPSTIME_MULTI-LASZIP_GPSTIME_MULTI_MINUS+1);
const int LASZIP_GPSTIME_MULTI_CODE_FULL=(LASZIP_GPSTIME_MULTI-LASZIP_GPSTIME_MULTI_MINUS+2);
const int LASZIP_GPSTIME_MULTI_TOTAL=(LASZIP_GPSTIME_MULTI-LASZIP_GPSTIME_MULTI_MINUS+6);
public LASwriteItemCompressed_GPSTIME11_v2(ArithmeticEncoder enc)
{
// set encoder
Debug.Assert(enc!=null);
this.enc=enc;
// create entropy models and integer compressors
m_gpstime_multi=enc.createSymbolModel(LASZIP_GPSTIME_MULTI_TOTAL);
m_gpstime_0diff=enc.createSymbolModel(6);
ic_gpstime=new IntegerCompressor(enc, 32, 9); // 32 bits, 9 contexts
}
public override bool init(laszip_point item)
{
// init state
last=0; next=0;
last_gpstime_diff[0]=0;
last_gpstime_diff[1]=0;
last_gpstime_diff[2]=0;
last_gpstime_diff[3]=0;
multi_extreme_counter[0]=0;
multi_extreme_counter[1]=0;
multi_extreme_counter[2]=0;
multi_extreme_counter[3]=0;
// init models and integer compressors
enc.initSymbolModel(m_gpstime_multi);
enc.initSymbolModel(m_gpstime_0diff);
ic_gpstime.initCompressor();
// init last item
last_gpstime[0].f64=item.gps_time;
last_gpstime[1].u64=0;
last_gpstime[2].u64=0;
last_gpstime[3].u64=0;
return true;
}
public override bool write(laszip_point item)
{
U64I64F64 this_gpstime=new U64I64F64();
this_gpstime.f64=item.gps_time;
if(last_gpstime_diff[last]==0) // if the last integer difference was zero
{
if(this_gpstime.i64==last_gpstime[last].i64)
{
enc.encodeSymbol(m_gpstime_0diff, 0); // the doubles have not changed
}
else
{
// calculate the difference between the two doubles as an integer
long curr_gpstime_diff_64=this_gpstime.i64-last_gpstime[last].i64;
int curr_gpstime_diff=(int)curr_gpstime_diff_64;
if(curr_gpstime_diff_64==(long)(curr_gpstime_diff))
{
enc.encodeSymbol(m_gpstime_0diff, 1); // the difference can be represented with 32 bits
ic_gpstime.compress(0, curr_gpstime_diff, 0);
last_gpstime_diff[last]=curr_gpstime_diff;
multi_extreme_counter[last]=0;
}
else // the difference is huge
{
// maybe the double belongs to another time sequence
for(uint i=1; i<4; i++)
{
long other_gpstime_diff_64=this_gpstime.i64-last_gpstime[(last+i)&3].i64;
int other_gpstime_diff=(int)other_gpstime_diff_64;
if(other_gpstime_diff_64==(long)(other_gpstime_diff))
{
enc.encodeSymbol(m_gpstime_0diff, i+2); // it belongs to another sequence
last=(last+i)&3;
return write(item);
}
}
// no other sequence found. start new sequence.
enc.encodeSymbol(m_gpstime_0diff, 2);
ic_gpstime.compress((int)(last_gpstime[last].u64>>32), (int)(this_gpstime.u64>>32), 8);
enc.writeInt((uint)(this_gpstime.u64));
next=(next+1)&3;
last=next;
last_gpstime_diff[last]=0;
multi_extreme_counter[last]=0;
}
last_gpstime[last].i64=this_gpstime.i64;
}
}
else // the last integer difference was *not* zero
{
if(this_gpstime.i64==last_gpstime[last].i64)
{
// if the doubles have not changed use a special symbol
enc.encodeSymbol(m_gpstime_multi, LASZIP_GPSTIME_MULTI_UNCHANGED);
}
else
{
// calculate the difference between the two doubles as an integer
long curr_gpstime_diff_64=this_gpstime.i64-last_gpstime[last].i64;
int curr_gpstime_diff=(int)curr_gpstime_diff_64;
// if the current gpstime difference can be represented with 32 bits
if(curr_gpstime_diff_64==(long)(curr_gpstime_diff))
{
// compute multiplier between current and last integer difference
double multi_f=(double)curr_gpstime_diff/(double)(last_gpstime_diff[last]);
int multi=MyDefs.I32_QUANTIZE(multi_f);
// compress the residual curr_gpstime_diff in dependance on the multiplier
if(multi==1)
{
// this is the case we assume we get most often for regular spaced pulses
enc.encodeSymbol(m_gpstime_multi, 1);
ic_gpstime.compress(last_gpstime_diff[last], curr_gpstime_diff, 1);
multi_extreme_counter[last]=0;
}
else if(multi>0)
{
if(multi<LASZIP_GPSTIME_MULTI) // positive multipliers up to LASZIP_GPSTIME_MULTI are compressed directly
{
enc.encodeSymbol(m_gpstime_multi, (uint)multi);
if(multi<10)
ic_gpstime.compress(multi*last_gpstime_diff[last], curr_gpstime_diff, 2);
else
ic_gpstime.compress(multi*last_gpstime_diff[last], curr_gpstime_diff, 3);
}
else
{
enc.encodeSymbol(m_gpstime_multi, LASZIP_GPSTIME_MULTI);
ic_gpstime.compress(LASZIP_GPSTIME_MULTI*last_gpstime_diff[last], curr_gpstime_diff, 4);
multi_extreme_counter[last]++;
if(multi_extreme_counter[last]>3)
{
last_gpstime_diff[last]=curr_gpstime_diff;
multi_extreme_counter[last]=0;
}
}
}
else if(multi<0)
{
if(multi>LASZIP_GPSTIME_MULTI_MINUS) // negative multipliers larger than LASZIP_GPSTIME_MULTI_MINUS are compressed directly
{
enc.encodeSymbol(m_gpstime_multi, (uint)(LASZIP_GPSTIME_MULTI-multi));
ic_gpstime.compress(multi*last_gpstime_diff[last], curr_gpstime_diff, 5);
}
else
{
enc.encodeSymbol(m_gpstime_multi, LASZIP_GPSTIME_MULTI-LASZIP_GPSTIME_MULTI_MINUS);
ic_gpstime.compress(LASZIP_GPSTIME_MULTI_MINUS*last_gpstime_diff[last], curr_gpstime_diff, 6);
multi_extreme_counter[last]++;
if(multi_extreme_counter[last]>3)
{
last_gpstime_diff[last]=curr_gpstime_diff;
multi_extreme_counter[last]=0;
}
}
}
else
{
enc.encodeSymbol(m_gpstime_multi, 0);
ic_gpstime.compress(0, curr_gpstime_diff, 7);
multi_extreme_counter[last]++;
if(multi_extreme_counter[last]>3)
{
last_gpstime_diff[last]=curr_gpstime_diff;
multi_extreme_counter[last]=0;
}
}
}
else // the difference is huge
{
// maybe the double belongs to another time sequence
for(uint i=1; i<4; i++)
{
long other_gpstime_diff_64=this_gpstime.i64-last_gpstime[(last+i)&3].i64;
int other_gpstime_diff=(int)other_gpstime_diff_64;
if(other_gpstime_diff_64==(long)(other_gpstime_diff))
{
// it belongs to this sequence
enc.encodeSymbol(m_gpstime_multi, LASZIP_GPSTIME_MULTI_CODE_FULL+i);
last=(last+i)&3;
return write(item);
}
}
// no other sequence found. start new sequence.
enc.encodeSymbol(m_gpstime_multi, LASZIP_GPSTIME_MULTI_CODE_FULL);
ic_gpstime.compress((int)(last_gpstime[last].u64>>32), (int)(this_gpstime.u64>>32), 8);
enc.writeInt((uint)(this_gpstime.u64));
next=(next+1)&3;
last=next;
last_gpstime_diff[last]=0;
multi_extreme_counter[last]=0;
}
last_gpstime[last].i64=this_gpstime.i64;
}
}
return true;
}
ArithmeticEncoder enc;
uint last, next;
U64I64F64[] last_gpstime=new U64I64F64[4];
int[] last_gpstime_diff=new int[4];
int[] multi_extreme_counter=new int[4];
ArithmeticModel m_gpstime_multi;
ArithmeticModel m_gpstime_0diff;
IntegerCompressor ic_gpstime;
}
}