/*private*/
void
DouglasPeuckerLineSimplifier::simplifySection(
std::size_t i,
std::size_t j)
{
if((i + 1) == j) {
return;
}
geos::geom::LineSegment seg(pts[i], pts[j]);
double maxDistance = -1.0;
std::size_t maxIndex = i;
for(std::size_t k = i + 1; k < j; k++) {
double distance = seg.distance(pts[k]);
if(distance > maxDistance) {
maxDistance = distance;
maxIndex = k;
}
}
if(maxDistance <= distanceTolerance) {
for(std::size_t k = i + 1; k < j; k++) {
usePt->operator[](k) = false;
}
}
else {
simplifySection(i, maxIndex);
simplifySection(maxIndex, j);
}
}
/*public*/
void
TaggedLineStringSimplifier::simplify(TaggedLineString* nLine)
{
assert(nLine);
line = nLine;
linePts = line->getParentCoordinates();
assert(linePts);
#if GEOS_DEBUG
std::cerr << "TaggedLineStringSimplifier[" << this << "] "
<< " TaggedLineString[" << line << "] "
<< " has " << linePts->size() << " coords in input"
<< std::endl;
#endif
simplifySection(0, linePts->size() - 1, 0);
}
/*public*/
DouglasPeuckerLineSimplifier::CoordsVectAutoPtr
DouglasPeuckerLineSimplifier::simplify()
{
CoordsVectAutoPtr coordList(new CoordsVect());
// empty coordlist is the simplest, won't simplify further
if(! pts.size()) {
return coordList;
}
usePt = BoolVectAutoPtr(new BoolVect(pts.size(), true));
simplifySection(0, pts.size() - 1);
for(std::size_t i = 0, n = pts.size(); i < n; ++i) {
if(usePt->operator[](i)) {
coordList->push_back(pts[i]);
}
}
// unique_ptr transfer ownership to its
// returned copy
return coordList;
}
/*private*/
void
TaggedLineStringSimplifier::simplifySection(size_t i,
size_t j, size_t depth)
{
depth += 1;
#if GEOS_DEBUG
std::cerr << "TaggedLineStringSimplifier[" << this << "] "
<< " simplifying section " << i << "-" << j
<< std::endl;
#endif
vector<size_t> sectionIndex(2);
if((i+1) == j)
{
#if GEOS_DEBUG
std::cerr << "single segment, no flattening"
<< std::endl;
#endif
auto_ptr<TaggedLineSegment> newSeg(new
TaggedLineSegment(*(line->getSegment(i))));
line->addToResult(newSeg);
// leave this segment in the input index, for efficiency
return;
}
bool isValidToSimplify = true;
/**
* Following logic ensures that there is enough points in the
* output line.
* If there is already more points than the minimum, there's
* nothing to check.
* Otherwise, if in the worst case there wouldn't be enough points,
* don't flatten this segment (which avoids the worst case scenario)
*/
if (line->getResultSize() < line->getMinimumSize())
{
size_t worstCaseSize = depth + 1;
if (worstCaseSize < line->getMinimumSize())
isValidToSimplify = false;
}
double distance;
// pass distance by ref
size_t furthestPtIndex = findFurthestPoint(linePts, i, j, distance);
#if GEOS_DEBUG
std::cerr << "furthest point " << furthestPtIndex
<< " at distance " << distance
<< std::endl;
#endif
// flattening must be less than distanceTolerance
if ( distance > distanceTolerance ) isValidToSimplify = false;
// test if flattened section would cause intersection
LineSegment candidateSeg(linePts->getAt(i), linePts->getAt(j));
sectionIndex[0] = i;
sectionIndex[1] = j;
if (hasBadIntersection(line, sectionIndex, candidateSeg))
isValidToSimplify = false;
if (isValidToSimplify)
{
auto_ptr<TaggedLineSegment> newSeg = flatten(i, j);
#if GEOS_DEBUG
std::cerr << "isValidToSimplify, adding seg "
<< newSeg->p0 << ", " << newSeg->p1
<< " to TaggedLineSegment["<<line<<"] result "
<< std::endl;
#endif
line->addToResult(newSeg);
return;
}
simplifySection(i, furthestPtIndex, depth);
simplifySection(furthestPtIndex, j, depth);
}
