ExternalVendorCode/tippecanoe
1
0
Fork 0
mirror of https://github.com/mapbox/tippecanoe.git synced 2025-03-23 04:15:15 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Add an option to guess the drop rate

Browse Source
This commit is contained in:
Eric Fischer 2015-12-16 12:13:24 -08:00
parent eb906dfc72
commit 6681817243
3 changed files with 43 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
README.md
View File

@ -69,7 +69,7 @@ Options
* -z _zoom_: Maxzoom: the highest zoom level for which tiles are generated (default 14)
* -Z _zoom_: Minzoom: the lowest zoom level for which tiles are generated (default 0)
* -B _zoom_: Base zoom, the level at and above which all points are included in the tiles (default maxzoom).
If you use -Bg, it will guess a zoom level that will keep less than 50,000 features in the densest tile.
If you use -Bg, it will guess a zoom level that will keep at most 50,000 features in the densest tile.
* -d _detail_: Detail at max zoom level (default 12, for tile resolution of 4096)
* -D _detail_: Detail at lower zoom levels (default 12, for tile resolution of 4096)
* -m _detail_: Minimum detail that it will try if tiles are too big at regular detail (default 7)
@ -83,7 +83,8 @@ Options
### Point simplification
* -r _rate_: Rate at which dots are dropped at zoom levels below basezoom (default 2.5)
* -r _rate_: Rate at which dots are dropped at zoom levels below basezoom (default 2.5).
If you use -rg, it will guess a drop rate that will keep at most 50,000 features in the densest tile.
* -g _gamma_: Rate at which especially dense dots are dropped (default 0, for no effect). A gamma of 2 reduces the number of dots less than a pixel apart to the square root of their original number.
### Doing more

48
geojson.c
View File

@ -1046,7 +1046,7 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
exit(EXIT_FAILURE);
}
if (basezoom < 0) {
if (basezoom < 0 || droprate < 0) {
struct index *map = mmap(NULL, indexpos, PROT_READ, MAP_PRIVATE, indexfd, 0);
if (map == MAP_FAILED) {
perror("mmap");
@ -1096,22 +1096,44 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
}
}
basezoom = MAX_ZOOM;
int z;
for (z = MAX_ZOOM; z >= 0; z--) {
if (tile[z].count > max[z].count) {
max[z] = tile[z];
}
if (max[z].count < 50000) {
basezoom = z;
}
// printf("%d/%u/%u %lld\n", z, max[z].x, max[z].y, max[z].count);
}
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);
#define MAX_FEATURES 50000
if (basezoom < 0) {
basezoom = MAX_ZOOM;
for (z = MAX_ZOOM; z >= 0; z--) {
if (max[z].count < MAX_FEATURES) {
basezoom = z;
}
// printf("%d/%u/%u %lld\n", z, max[z].x, max[z].y, max[z].count);
}
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) {
droprate = 1;
for (z = 0; z <= basezoom; z++) {
double interval = exp(log(droprate) * (basezoom - z));
if (max[z].count / interval >= MAX_FEATURES) {
interval = (long double) max[z].count / MAX_FEATURES;
droprate = exp(log(interval) / (basezoom - z));
interval = exp(log(droprate) * (basezoom - z));
fprintf(stderr, "Choosing a drop rate of -r%f to keep %f features in tile %d/%u/%u.\n", droprate, max[z].count / interval, z, max[z].x, max[z].y);
}
}
}
munmap(map, indexpos);
}
@ -1375,7 +1397,11 @@ int main(int argc, char **argv) {
break;
case 'r':
droprate = atof(optarg);
if (strcmp(optarg, "g") == 0) {
droprate = -2;
} else {
droprate = atof(optarg);
}
break;
case 'b':

5
man/tippecanoe.1
View File

@ -76,7 +76,7 @@ specified, the files are all merged into the single named layer.
\-Z \fIzoom\fP: Minzoom: the lowest zoom level for which tiles are generated (default 0)
.IP \(bu 2
\-B \fIzoom\fP: Base zoom, the level at and above which all points are included in the tiles (default maxzoom).
If you use \-Bg, it will guess a zoom level that will keep less than 50,000 features in the densest tile.
If you use \-Bg, it will guess a zoom level that will keep at most 50,000 features in the densest tile.
.IP \(bu 2
\-d \fIdetail\fP: Detail at max zoom level (default 12, for tile resolution of 4096)
.IP \(bu 2
@ -98,7 +98,8 @@ If you use \-Bg, it will guess a zoom level that will keep less than 50,000 feat
.SS Point simplification
.RS
.IP \(bu 2
\-r \fIrate\fP: Rate at which dots are dropped at zoom levels below basezoom (default 2.5)
\-r \fIrate\fP: Rate at which dots are dropped at zoom levels below basezoom (default 2.5).
If you use \-rg, it will guess a drop rate that will keep at most 50,000 features in the densest tile.
.IP \(bu 2
\-g \fIgamma\fP: Rate at which especially dense dots are dropped (default 0, for no effect). A gamma of 2 reduces the number of dots less than a pixel apart to the square root of their original number.
.RE