Add an option to drop a fraction of polygons by zoom.

Only warn once about polygon cleaning failures.

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.9.9
+
+* Add --drop-polygons to drop a fraction of polygons by zoom level
+* Only complain once about failing to clean polygons
+
 ## 1.9.8
 
 * Use an on-disk radix sort for the index to control virtual memory thrashing

README.md

@@ -113,6 +113,7 @@ resolution is obtained than by using a smaller _maxzoom_ or _detail_.
  * -ar or --reverse: Try reversing the directions of lines to make them coalesce and compress better
  * -ao or --reorder: Reorder features to put ones with the same properties in sequence, to try to get them to coalesce
  * -al or --drop-lines: Let "dot" dropping at lower zooms apply to lines too
+ * -ap or --drop-polygons: Let "dot" dropping at lower zooms apply to polygons too
 
 ### Doing less
 

geojson.c

@@ -2396,6 +2396,7 @@ int main(int argc, char **argv) {
 		{"reverse", no_argument, &additional[A_REVERSE], 1},
 		{"reorder", no_argument, &additional[A_REORDER], 1},
 		{"drop-lines", no_argument, &additional[A_LINE_DROP], 1},
+		{"drop-polygons", no_argument, &additional[A_POLYGON_DROP], 1},
 		{"prefer-radix-sort", no_argument, &additional[A_PREFER_RADIX_SORT], 1},
 
 		{"no-line-simplification", no_argument, &prevent[P_SIMPLIFY], 1},

geometry.cc

@@ -311,7 +311,12 @@ drawvec clean_or_clip_poly(drawvec &geom, int z, int detail, int buffer, bool cl
 		}
 
 		if (!clipper.Execute(ClipperLib::ctUnion, clipped)) {
-			fprintf(stderr, "Polygon clean failed\n");
+			static bool complained = false;
+
+			if (!complained) {
+				fprintf(stderr, "Polygon clean failed\n");
+				complained = true;
+			}
 		}
 	}
 

man/tippecanoe.1

@@ -138,6 +138,8 @@ compensate for the larger marker, or \-rf\fInumber\fP to allow at most \fInumber
 \-ao or \-\-reorder: Reorder features to put ones with the same properties in sequence, to try to get them to coalesce
 .IP \(bu 2
 \-al or \-\-drop\-lines: Let "dot" dropping at lower zooms apply to lines too
+.IP \(bu 2
+\-ap or \-\-drop\-polygons: Let "dot" dropping at lower zooms apply to polygons too
 .RE
 .SS Doing less
 .RS

tile.cc

@@ -793,7 +793,9 @@ long long write_tile(char **geoms, char *metabase, char *stringpool, int z, unsi
 				continue;
 			}
 
-			if (gamma >= 0 && (t == VT_POINT || (additional[A_LINE_DROP] && t == VT_LINE))) {
+			if (gamma >= 0 && (t == VT_POINT ||
+					   (additional[A_LINE_DROP] && t == VT_LINE) ||
+					   (additional[A_POLYGON_DROP] && t == VT_POLYGON))) {
 				seq++;
 				if (seq >= 0) {
 					seq -= interval;

tile.h

@@ -46,6 +46,8 @@ static int additional_options[] = {
 	A_REORDER,
 #define A_LINE_DROP ((int) 'l')
 	A_LINE_DROP,
+#define A_POLYGON_DROP ((int) 'p')
+	A_POLYGON_DROP,
 #define A_PREFER_RADIX_SORT ((int) 'r')
 	A_PREFER_RADIX_SORT,
 };

version.h

@@ -1 +1 @@
-#define VERSION "tippecanoe v1.9.8\n"
+#define VERSION "tippecanoe v1.9.9\n"