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Heuristics for basezoom and droprate if no tiles are naturally small enough

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This commit is contained in:
Eric Fischer 2015-12-16 16:18:16 -08:00
parent 38fe00c7ab
commit f9d1e87360
1 changed files with 29 additions and 2 deletions
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31
geojson.c
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@ -1140,6 +1140,7 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
#define MAX_FEATURES 50000
int obasezoom = basezoom;
if (basezoom < 0) {
basezoom = MAX_ZOOM;
@ -1154,10 +1155,36 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
fprintf(stderr, "Choosing a base zoom of -B%d to keep %lld features in tile %d/%u/%u.\n", basezoom, max[basezoom].count, basezoom, max[basezoom].x, max[basezoom].y);
}
if (droprate < 0) {
if (obasezoom < 0 && basezoom > maxzoom) {
fprintf(stderr, "Couldn't find a suitable base zoom. Working from the other direction.\n");
if (gamma == 0) {
fprintf(stderr, "You might want to try -g1 to limit near-duplicates.\n");
}
if (droprate < 0) {
if (maxzoom == 0) {
droprate = 2.5;
} else {
droprate = exp(log((long double) max[0].count / max[maxzoom].count) / (maxzoom));
fprintf(stderr, "Choosing a drop rate of -r%f to get from %lld to %lld in %d zooms\n", droprate, max[maxzoom].count, max[0].count, maxzoom);
}
}
basezoom = 0;
for (z = 0; z <= maxzoom; z++) {
// printf("%d/%u/%u has %lld ", z, max[z].x, max[z].y, max[z].count);
double zoomdiff = log((long double) max[z].count / MAX_FEATURES) / log(droprate);
// printf("which implies that base zoom should be %f\n", zoomdiff + z);
if (zoomdiff + z > basezoom) {
basezoom = ceil(zoomdiff + z);
}
}
fprintf(stderr, "Choosing a base zoom of -B%d to keep %f features in tile %d/%u/%u.\n", basezoom, max[maxzoom].count * exp(log(droprate) * (maxzoom - basezoom)), maxzoom, max[maxzoom].x, max[maxzoom].y);
} else if (droprate < 0) {
droprate = 1;
for (z = basezoom; z >= 0; z--) {
for (z = basezoom - 1; z >= 0; z--) {
double interval = exp(log(droprate) * (basezoom - z));
if (max[z].count / interval >= MAX_FEATURES) {