com.ctreber.acearth.scanbit.BitGeneratorMapDefault Maven / Gradle / Ivy
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package com.ctreber.acearth.scanbit;
import java.util.Comparator;
import com.ctreber.acearth.projection.Projection;
import com.ctreber.acearth.util.EdgeCrossing;
import com.ctreber.acearth.util.Point2D;
import com.ctreber.acearth.util.Point3D;
/**
* Map scanner for mercator and cylindrical projections.
*
*
© 2002 Christian Treber, [email protected]
* @author Christian Treber, [email protected]
*
*/
public class BitGeneratorMapDefault extends BitGeneratorMap
{
public BitGeneratorMapDefault(Projection pProjection)
{
super(pProjection);
}
protected Comparator getEdgeXingComparator()
{
return new EdgeXingComparator();
}
/**
* Seems to: walk along outline of projected area.
*/
protected ScanBuf scanOutline()
{
final ScanBuf lScanBuf = new ScanBuf(fImageHeight, fImageWidth);
final double lLeft = fProjection.finalizeX(-Math.PI);
final double lRight = fProjection.finalizeX(Math.PI);
// Will be adjusted to fit height.
final double lTop = fProjection.finalizeY(1e6);
final double lBottom = fProjection.finalizeY(-1e6);
// Top
lScanBuf.addLine(lRight, lTop, lLeft, lTop);
// Left
lScanBuf.addLine(lLeft, lTop, lLeft, lBottom);
// Bottom
lScanBuf.addLine(lLeft, lBottom, lRight, lBottom);
// Right
lScanBuf.addLine(lRight, lBottom, lRight, lTop);
return lScanBuf;
}
/**
*
Look at 2 neighboring points in polygon and find edge crossings -
* edge of the globe?! Edge of image?
*/
protected void scanPolygon(ScanBuf pScanBuf,
Point3D[] pPoints3D, Point2D[] pPoints2D, int pIndex)
{
final Point2D lCurr = pPoints2D[pIndex];
final int lIndexPrev = pIndex - 1 >= 0 ? pIndex - 1 : pPoints2D.length - 1;
final Point2D lPrev = pPoints2D[lIndexPrev];
double dx = lCurr.getX() - lPrev.getX();
if(Math.abs(dx) <= Math.PI)
{
// Perimeter not crossed.
pScanBuf.addLine(
fProjection.finalizeX(lPrev.getX()), fProjection.finalizeY(lPrev.getY()),
fProjection.finalizeX(lCurr.getX()), fProjection.finalizeY(lCurr.getY()));
return;
}
// Perimeter crossed, we need to wrap the line around the edge.
int lAngle;
double mx;
double my = getYMidPoint(pPoints3D[lIndexPrev], pPoints3D[pIndex]);
if(dx > 0)
{
// Curve runs right
mx = -Math.PI;
lAngle = 2;
} else
{
mx = Math.PI;
lAngle = 0;
}
// From previous point to edge...
pScanBuf.addLine(
fProjection.finalizeX(lPrev.getX()), fProjection.finalizeY(lPrev.getY()),
fProjection.finalizeX(mx), fProjection.finalizeY(my));
addEdgeXing(new EdgeCrossing(EdgeCrossing.XingTypeExit, pIndex, mx, my, lAngle));
if(dx > 0)
{
mx = Math.PI;
lAngle = 0;
} else
{
mx = -Math.PI;
lAngle = 2;
}
// ...and from edge to current point.
pScanBuf.addLine(
fProjection.finalizeX(mx), fProjection.finalizeY(my),
fProjection.finalizeX(lCurr.getX()), fProjection.finalizeY(lCurr.getY()));
addEdgeXing(new EdgeCrossing(EdgeCrossing.XingTypeEntry, pIndex, mx, my, lAngle));
}
/**
*
My educated guess is that the mid point between the current and
* the previous point is calculated, and - kind of - y of that point
* is returned.
*/
private double getYMidPoint(Point3D pPrev, Point3D pCurr)
{
double lY;
final double lZ;
if(pCurr.getX() != 0)
{
// if xPrev is twice xCurr, ratio is 2
double ratio = (pPrev.getX() / pCurr.getX());
lY = pPrev.getY() - ratio * pCurr.getY();
lZ = pPrev.getZ() - ratio * pCurr.getZ();
} else
{
lY = pCurr.getY();
lZ = pCurr.getZ();
}
final double lDistance = Math.sqrt((lY * lY) + (lZ * lZ));
lY *= ((lZ > 0) ? -1 : 1) / lDistance;
return fProjection.projectY(lY);
}
/**
*
Side effect: Creates ScanBuf lines.
*/
protected void handleCrossings(ScanBuf pScanBuf, EdgeCrossing[] xings)
{
EdgeCrossing from;
EdgeCrossing to;
int lStart;
if(xings[0].getType() == EdgeCrossing.XingTypeExit)
{
lStart = 0;
} else
{
// Type "entry".
from = xings[xings.length - 1];
to = xings[0];
addEdgeToScanbuf(pScanBuf, from, to);
lStart = 1;
}
for(int i = lStart; i < xings.length - 1; i += 2)
{
from = xings[i];
to = xings[i + 1];
addEdgeToScanbuf(pScanBuf, from, to);
}
}
/**
*
For handleCrossing(). Side effect: Creates ScanBuf lines.
*
* @param pScanBuf
* @param from
* @param to
*/
private void addEdgeToScanbuf(ScanBuf pScanBuf, EdgeCrossing from,
EdgeCrossing to)
{
int lAngleFrom = (int)from.getAngle();
double lXFrom = fProjection.finalizeX(from.getX());
double lYFrom = fProjection.finalizeY(from.getY());
// Step around in 90 degree increments until target angle is reached
while(lAngleFrom != (int)to.getAngle())
{
int lAngleNew = 0;
double lXNew = 0;
double lYNew = 0;
switch(lAngleFrom)
{
case 0:
// Top right
lXNew = fProjection.finalizeX(Math.PI);
lYNew = fProjection.finalizeY(1e6);
lAngleNew = 1;
break;
case 1:
// Top left
lXNew = fProjection.finalizeX(-Math.PI);
lYNew = fProjection.finalizeY(1e6);
lAngleNew = 2;
break;
case 2:
// Bottom left
lXNew = fProjection.finalizeX(-Math.PI);
lYNew = fProjection.finalizeY(-1e6);
lAngleNew = 3;
break;
case 3:
// Bottom right
lXNew = fProjection.finalizeX(Math.PI);
lYNew = fProjection.finalizeY(-1e6);
lAngleNew = 0;
break;
}
pScanBuf.addLine(lXFrom, lYFrom, lXNew, lYNew);
lAngleFrom = lAngleNew;
lXFrom = lXNew;
lYFrom = lYNew;
}
// ...and from last to final.
pScanBuf.addLine(lXFrom, lYFrom, fProjection.finalizeX(to.getX()),
fProjection.finalizeY(to.getY()));
}
private static class EdgeXingComparator implements Comparator
{
public int compare(Object o1, Object o2)
{
final EdgeCrossing a = (EdgeCrossing)o1;
final EdgeCrossing b = (EdgeCrossing)o2;
if(a.getAngle() < b.getAngle())
{
return -1;
}
if(a.getAngle() > b.getAngle())
{
return 1;
}
// Angles are equal.
if(a.getAngle() == 0)
{
return (a.getY() < b.getY()) ? -1 : (a.getY() > b.getY()) ? 1 : 0;
}
if(a.getAngle() == 2)
{
return (a.getY() > b.getY()) ? -1 : (a.getY() < b.getY()) ? 1 : 0;
}
throw new RuntimeException("No result");
}
}
}