From 93d0767829c9da99cb1fbc7f97f4cb7ec793b7e5 Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Fri, 8 Jan 2016 11:31:10 -0800
Subject: [PATCH] Add an option to do line simplification only at zooms below
 maxzoom

---
 README.md        | 1 +
 man/tippecanoe.1 | 2 ++
 tile.cc          | 5 ++++-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 8620c32..62140e1 100644
--- a/README.md
+++ b/README.md
@@ -106,6 +106,7 @@ Options
 ### Doing less
 
  * -ps: Don't simplify lines
+ * -pS: Don't simplify lines at maxzoom (but do simplify at lower zooms)
  * -pf: Don't limit tiles to 200,000 features
  * -pk: Don't limit tiles to 500K bytes
  * -pd: Dynamically drop some fraction of features from large tiles to keep them under the 500K size limit. It will probably look ugly at the tile boundaries.
diff --git a/man/tippecanoe.1 b/man/tippecanoe.1
index f8a3798..765a740 100644
--- a/man/tippecanoe.1
+++ b/man/tippecanoe.1
@@ -130,6 +130,8 @@ If you use \-rg, it will guess a drop rate that will keep at most 50,000 feature
 .IP \(bu 2
 \-ps: Don't simplify lines
 .IP \(bu 2
+\-pS: Don't simplify lines at maxzoom (but do simplify at lower zooms)
+.IP \(bu 2
 \-pf: Don't limit tiles to 200,000 features
 .IP \(bu 2
 \-pk: Don't limit tiles to 500K bytes
diff --git a/tile.cc b/tile.cc
index 670435a..7cc613d 100644
--- a/tile.cc
+++ b/tile.cc
@@ -479,6 +479,7 @@ struct partial {
 	int line_detail;
 	char *prevent;
 	char *additional;
+	int maxzoom;
 };
 
 struct partial_arg {
@@ -499,8 +500,9 @@ void *partial_feature_worker(void *v) {
 		int line_detail = (*partials)[i].line_detail;
 		char *prevent = (*partials)[i].prevent;
 		char *additional = (*partials)[i].additional;
+		int maxzoom = (*partials)[i].maxzoom;
 
-		if ((t == VT_LINE || t == VT_POLYGON) && !prevent['s' & 0xFF]) {
+		if ((t == VT_LINE || t == VT_POLYGON) && !(prevent['s' & 0xFF] || (z == maxzoom && prevent['S' & 0xFF]))) {
 			if (1 /* !reduced */) {  // XXX why did this not simplify if reduced?
 				if (t == VT_LINE) {
 					geom = remove_noop(geom, t, 32 - z - line_detail);
@@ -806,6 +808,7 @@ long long write_tile(char **geoms, char *metabase, char *stringpool, int z, unsi
 				p.line_detail = line_detail;
 				p.prevent = prevent;
 				p.additional = additional;
+				p.maxzoom = maxzoom;
 				partials.push_back(p);
 			}
 		}