From a185073f0abea557a9ab11a23a4219aaaad2ea0a Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Thu, 18 Jun 2015 14:16:16 -0700
Subject: [PATCH] Shrink the geometry by shaving off bits below the maxzoom
 tile resolution

---
 geojson.c   | 10 +++++++---
 geometry.cc |  4 ++--
 tile.cc     |  4 ++--
 tile.h      |  1 +
 4 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/geojson.c b/geojson.c
index d43b0db2..c381e95c 100644
--- a/geojson.c
+++ b/geojson.c
@@ -26,6 +26,7 @@ int full_detail = -1;
 int min_detail = 7;
 
 unsigned initial_x = 0, initial_y = 0;
+int geometry_scale = 0;
 int initialized = 0;
 
 #define GEOM_POINT 0	   /* array of positions */
@@ -164,8 +165,8 @@ void parse_geometry(int t, json_object *j, unsigned *bbox, long long *fpos, FILE
 			}
 
 			serialize_byte(out, op, fpos, fname);
-			serialize_long_long(out, x - *wx, fpos, fname);
-			serialize_long_long(out, y - *wy, fpos, fname);
+			serialize_long_long(out, (x >> geometry_scale) - (*wx >> geometry_scale), fpos, fname);
+			serialize_long_long(out, (y >> geometry_scale) - (*wy >> geometry_scale), fpos, fname);
 			*wx = x;
 			*wy = y;
 		} else {
@@ -494,7 +495,7 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
 	long long indexpos = 0;
 
 	unlink(metaname);
-	unlink(poolname);
+	//unlink(poolname);
 	unlink(geomname);
 	unlink(indexname);
 
@@ -1182,6 +1183,9 @@ int main(int argc, char **argv) {
 		exit(EXIT_FAILURE);
 	}
 
+	geometry_scale = 32 - (full_detail + maxzoom);
+	printf("geometry scale is %d\n", geometry_scale);
+
 	if (outdir == NULL) {
 		fprintf(stderr, "%s: must specify -o out.mbtiles\n", argv[0]);
 		exit(EXIT_FAILURE);
diff --git a/geometry.cc b/geometry.cc
index 14d489d2..281a41ca 100644
--- a/geometry.cc
+++ b/geometry.cc
@@ -41,8 +41,8 @@ drawvec decode_geometry(char **meta, int z, unsigned tx, unsigned ty, int detail
 			deserialize_long_long(meta, &dx);
 			deserialize_long_long(meta, &dy);
 
-			wx += dx;
-			wy += dy;
+			wx += dx << geometry_scale;
+			wy += dy << geometry_scale;
 
 			long long wwx = wx;
 			long long wwy = wy;
diff --git a/tile.cc b/tile.cc
index 2877da45..585783fe 100644
--- a/tile.cc
+++ b/tile.cc
@@ -510,8 +510,8 @@ long long write_tile(char **geoms, char *metabase, char *stringpool, unsigned *f
 								serialize_byte(geomfile[j], geom[u].op, &geompos[j], fname);
 
 								if (geom[u].op != VT_CLOSEPATH) {
-									serialize_long_long(geomfile[j], geom[u].x + sx - wx, &geompos[j], fname);
-									serialize_long_long(geomfile[j], geom[u].y + sy - wy, &geompos[j], fname);
+									serialize_long_long(geomfile[j], ((geom[u].x + sx) >> geometry_scale) - (wx >> geometry_scale), &geompos[j], fname);
+									serialize_long_long(geomfile[j], ((geom[u].y + sy) >> geometry_scale) - (wy >> geometry_scale), &geompos[j], fname);
 									wx = geom[u].x + sx;
 									wy = geom[u].y + sy;
 								}
diff --git a/tile.h b/tile.h
index bccc1450..644662e1 100644
--- a/tile.h
+++ b/tile.h
@@ -28,3 +28,4 @@ struct pool_val *deserialize_string(char **f, struct pool *p, int type);
 long long write_tile(char **geom, char *metabase, char *stringpool, unsigned *file_bbox, int z, unsigned x, unsigned y, int detail, int min_detail, int basezoom, struct pool **file_keys, char **layernames, sqlite3 *outdb, double droprate, int buffer, const char *fname, FILE *geomfile[4], int file_minzoom, int file_maxzoom, double todo, char *geomstart, long long along, double gamma, int nlayers, char *prevent);
 
 extern unsigned initial_x, initial_y;
+extern int geometry_scale;