WebSVN - mkgmap - Rev 3408 - /u/mike.b/main/src/uk/me/parabola/imgfmt/app/trergn/LinePreparer.java

/**
* Copyright (C) 2006 Steve Ratcliffe
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Author: steve
* Date: 24-Dec-2006
*/
package uk.me.parabola.imgfmt.app.trergn;

import java.util.List;

import uk.me.parabola.imgfmt.app.BitWriter;
import uk.me.parabola.imgfmt.app.Coord;
import uk.me.parabola.log.Logger;

/**
* This class holds all of the calculations needed to encode a line into
* the garmin format.
*/
public class LinePreparer {
private static final Logger log = Logger.getLogger(LinePreparer.class);

// These are our inputs.
private final Polyline polyline;

private boolean extraBit;
private final boolean extTypeLine;
private boolean xSameSign;
private boolean xSignNegative; // Set if all negative

private boolean ySameSign;
private boolean ySignNegative; // Set if all negative

// The base number of bits
private int xBase;
private int yBase;

// The delta changes between the points.
private int[] deltas;
private boolean[] nodes;

LinePreparer(Polyline line) {
if (line.isRoad() &&
line.getSubdiv().getZoom().getLevel() == 0 &&
line.roadHasInternalNodes()) {
// it might be safe to write the extra bits regardless,
// but who knows
extraBit = true;
}

extTypeLine = line.hasExtendedType();

polyline = line;
calcLatLong();
calcDeltas();
}

/**
* Write the bit stream to a BitWriter and return it.
*
* @return A class containing the written byte stream.
*/
public BitWriter makeBitStream(int minPointsRequired) {

assert xBase >= 0 && yBase >= 0;

int xbits = 2;
if (xBase < 10)
xbits += xBase;
else
xbits += (2 * xBase) - 9;

int ybits = 2;
if (yBase < 10)
ybits += yBase;
else
ybits += (2 * yBase) - 9;

// Note no sign included.
if (log.isDebugEnabled())
log.debug("xbits", xbits, ", y=", ybits);

// Write the bitstream
BitWriter bw = new BitWriter();

// Pre bit stream info
bw.putn(xBase, 4);
bw.putn(yBase, 4);

bw.put1(xSameSign);
if (xSameSign)
bw.put1(xSignNegative);

bw.put1(ySameSign);
if (ySameSign)
bw.put1(ySignNegative);

if (log.isDebugEnabled()) {
log.debug("x same is", xSameSign, "sign is", xSignNegative);
log.debug("y same is", ySameSign, "sign is", ySignNegative);
}

if(extTypeLine) {
bw.put1(false); // no extra bits required
}

// first extra bit always appears to be false
// refers to the start point?
if (extraBit)
bw.put1(false);

int numPointsEncoded = 1;
for (int i = 0; i < deltas.length; i+=2) {
int dx = deltas[i];
int dy = deltas[i + 1];
if (dx == 0 && dy == 0){
if (extraBit && nodes[i/2+1] == false && i+2 != deltas.length) // don't skip CoordNode
continue;
}
++numPointsEncoded;

if (log.isDebugEnabled())
log.debug("x delta", dx, "~", xbits);
assert dx >> xbits == 0 || dx >> xbits == -1;
if (xSameSign) {
bw.putn(Math.abs(dx), xbits);
} else {
// catch inadvertent output of "magic" value that has
// sign bit set but other bits all 0
assert dx >= 0 || (dx & ((1 << xbits) - 1)) != 0;
bw.putn(dx, xbits);
bw.put1(dx < 0);
}

if (log.isDebugEnabled())
log.debug("y delta", dy, ybits);
assert dy >> ybits == 0 || dy >> ybits == -1;
if (ySameSign) {
bw.putn(Math.abs(dy), ybits);
} else {
// catch inadvertent output of "magic" value that has
// sign bit set but other bits all 0
assert dy >= 0 || (dy & ((1 << ybits) - 1)) != 0;
bw.putn(dy, ybits);
bw.put1(dy < 0);
}
if (extraBit)
bw.put1(nodes[i/2+1]);
}

if (log.isDebugEnabled())
log.debug(bw);

if(numPointsEncoded < minPointsRequired)
return null;

return bw;
}

/**
* Calculate the correct lat and long points. They must be shifted if
* required by the zoom level. The point that is taken to be the
* location is just the first point in the line.
*/
private void calcLatLong() {
Coord co = polyline.getPoints().get(0);

polyline.setLatitude(co.getLatitude());
polyline.setLongitude(co.getLongitude());
}

/**
* Calculate the deltas of one point to the other. While we are doing
* this we must save more information about the maximum sizes, if they
* are all the same sign etc. This must be done separately for both
* the lat and long values.
*/
private void calcDeltas() {
Subdivision subdiv = polyline.getSubdiv();
if(log.isDebugEnabled())
log.debug("label offset", polyline.getLabel().getOffset());
int shift = subdiv.getShift();
List<Coord> points = polyline.getPoints();

// Space to hold the deltas
int numPointsToUse = points.size();
if (polyline instanceof Polygon){
if (points.get(0).equals(points.get(points.size()-1)))
--numPointsToUse; // no need to write the closing point
}
deltas = new int[2 * (numPointsToUse - 1)];

if (extraBit)
nodes = new boolean[numPointsToUse];
boolean first = true;

// OK go through the points
int lastLat = 0;
int lastLong = 0;
boolean xDiffSign = false; // The long values have different sign
boolean yDiffSign = false; // The lat values have different sign
int xSign = 0; // If all the same sign, then this 1 or -1 depending on +ve or -ve
int ySign = 0; // As above for lat.
int minDx = Integer.MAX_VALUE, maxDx = 0;
int minDy = Integer.MAX_VALUE, maxDy = 0;
// index of first point in a series of identical coords (after shift)
int firstsame = 0;
for (int i = 0; i < numPointsToUse; i++) {
Coord co = points.get(i);

int lat = subdiv.roundLatToLocalShifted(co.getLatitude());
int lon = subdiv.roundLonToLocalShifted(co.getLongitude());
if (log.isDebugEnabled())
log.debug("shifted pos", lat, lon);
if (first) {
lastLat = lat;
lastLong = lon;
first = false;
continue;
}

// compute normalized differences
// -2^(shift-1) <= dx, dy < 2^(shift-1)
// XXX: relies on the fact that java integers are 32 bit signed
final int offset = 8+shift;
int dx = (lon - lastLong) << offset >> offset;
int dy = (lat - lastLat) << offset >> offset;
assert (dx == 0 && lon != lastLong) == false: ("delta lon too large: " + (lon - lastLong));
assert (dy == 0 && lat != lastLat) == false: ("delta lat too large: " + (lat - lastLat));
lastLong = lon;
lastLat = lat;

if (dx != 0 || dy != 0 || (extraBit && co.getId() != 0))
firstsame = i;

/*
* Current thought is that the node indicator is set when
* the point is a node. There's a separate first extra bit
* that always appears to be false. The last points' extra bit
* is set if the point is a node and this is not the last
* polyline making up the road.
* Todo: special case the last bit
*/
if (extraBit) {
boolean extra = false;
if (co.getId() != 0) {
if (i < nodes.length - 1)
// inner node of polyline
extra = true;
else
// end node of polyline: set if inner
// node of road
extra = !polyline.isLastSegment();
}

/*
* Only the first among a range of equal points
* is written, so set the bit if any of the points
* is a node.
* Since we only write extra bits at level 0 now,
* this can only happen when points in the input
* data round to the same point in map units, so
* it may be better to handle this in the
* reader.
*/
nodes[firstsame] = nodes[firstsame] || extra;
}

// See if they can all be the same sign.
if (!xDiffSign) {
int thisSign = (dx >= 0)? 1: -1;
if (xSign == 0) {
xSign = thisSign;
} else if (thisSign != xSign) {
// The signs are different
xDiffSign = true;
}
}
if (!yDiffSign) {
int thisSign = (dy >= 0)? 1: -1;
if (ySign == 0) {
ySign = thisSign;
} else if (thisSign != ySign) {
// The signs are different
yDiffSign = true;
}
}

// find largest delta values
if (dx < minDx)
minDx = dx;
if (dx > maxDx)
maxDx = dx;
if (dy < minDy)
minDy = dy;
if (dy > maxDy)
maxDy = dy;

// Save the deltas
deltas[2*(i-1)] = dx;
deltas[2*(i-1) + 1] = dy;
}
// Find the maximum number of bits required to hold the delta values.
int xBits = Math.max(bitsNeeded(minDx), bitsNeeded(maxDx));
int yBits = Math.max(bitsNeeded(minDy), bitsNeeded(maxDy));

// Now we need to know the 'base' number of bits used to represent
// the value. In decoding you start with that number and add various
// adjustments to get the final value. We need to try and work
// backwards from this.
//
// I don't care about getting the smallest possible file size so
// err on the side of caution.
//
// Note that the sign bit is already not included so there is
// no adjustment needed for it.

if (log.isDebugEnabled())
log.debug("initial xBits, yBits", xBits, yBits);

if (xBits < 2)
xBits = 2;
int tmp = xBits - 2;
if (tmp > 10) {
if ((tmp & 0x1) == 0)
tmp++;
tmp = 9 + (tmp - 9) / 2;
}
this.xBase = tmp;

if (yBits < 2)
yBits = 2;
tmp = yBits - 2;
if (tmp > 10) {
if ((tmp & 0x1) == 0)
tmp++;
tmp = 9 + (tmp - 9) / 2;
}
this.yBase = tmp;

if (log.isDebugEnabled())
log.debug("initial xBase, yBase", xBase, yBase);

// Set flags for same sign etc.
this.xSameSign = !xDiffSign;
this.ySameSign = !yDiffSign;
this.xSignNegative = xSign < 0;
this.ySignNegative = ySign < 0;
}

/**
* The bits needed to hold a number without truncating it.
*
* @param val The number for bit counting.
* @return The number of bits required.
*/
public static int bitsNeeded(int val) {
int n = Math.abs(val);

int count = val < 0? 1: 0;
while (n != 0) {
n >>>= 1;
count++;
}
return count;
}

public boolean isExtraBit() {
return extraBit;
}

}

Subversion Repositories mkgmap

(root)/u/mike.b/main/src/uk/me/parabola/imgfmt/app/trergn/LinePreparer.java - Rev 3408