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Tiny polygons (smaller than a pixel) decay into probabilities.

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This commit is contained in:
Eric Fischer 2014-10-07 15:37:55 -07:00
parent adbd9f6edb
commit 49b36e09cc
1 changed files with 66 additions and 1 deletions
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65
tile.cc
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@ -506,6 +506,63 @@ drawvec clip_poly(drawvec &geom, int z, int detail) {
return out;
}
drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double *accum_area) {
drawvec out;
long long pixel = 1 << (32 - detail - z);
*reduced = true;
for (unsigned i = 0; i < geom.size(); i++) {
if (geom[i].op == VT_MOVETO) {
unsigned j;
for (j = i + 1; j < geom.size(); j++) {
if (geom[j].op == VT_CLOSEPATH) {
break;
}
}
double area = 0;
for (unsigned k = i; k < j; k++) {
area += geom[k].x * geom[i + ((k - i + 1) % (j - i))].y;
area -= geom[k].y * geom[i + ((k - i + 1) % (j - i))].x;
}
area = fabs(area / 2);
if (area <= pixel * pixel) {
//printf("area is only %f vs %lld so using square\n", area, pixel * pixel);
*accum_area += area;
if (*accum_area > pixel * pixel) {
// XXX use centroid;
out.push_back(draw(VT_MOVETO, geom[i].x, geom[i].y));
out.push_back(draw(VT_LINETO, geom[i].x + pixel, geom[i].y));
out.push_back(draw(VT_LINETO, geom[i].x + pixel, geom[i].y + pixel));
out.push_back(draw(VT_LINETO, geom[i].x, geom[i].y + pixel));
out.push_back(draw(VT_CLOSEPATH, geom[i].x, geom[i].y));
*accum_area -= pixel * pixel;
}
} else {
//printf("area is %f so keeping instead of %lld\n", area, pixel * pixel);
for (unsigned k = i; k <= j && k < geom.size(); k++) {
out.push_back(geom[k]);
}
*reduced = false;
}
i = j;
} else {
out.push_back(geom[i]);
}
}
return out;
}
drawvec clip_lines(drawvec &geom, int z, int detail) {
drawvec out;
unsigned i;
@ -665,6 +722,7 @@ long long write_tile(struct index *start, struct index *end, char *metabase, uns
double seq = 0;
long long count = 0;
long long along = 0;
double accum_area = 0;
if (z < basezoom) {
interval = exp(log(droprate) * (basezoom - z));
@ -691,6 +749,11 @@ long long write_tile(struct index *start, struct index *end, char *metabase, uns
drawvec geom = decode_feature(&meta, z, tx, ty, line_detail);
bool reduced = false;
if (t == VT_POLYGON) {
geom = reduce_tiny_poly(geom, z, line_detail, &reduced, &accum_area);
}
if (t == VT_LINE) {
geom = clip_lines(geom, z, line_detail);
}
@ -700,8 +763,10 @@ long long write_tile(struct index *start, struct index *end, char *metabase, uns
}
if (t == VT_LINE || t == VT_POLYGON) {
if (!reduced) {
geom = simplify_lines(geom, z, line_detail);
}
}
#if 0
if (t == VT_LINE && z != basezoom) {