From 17a73b1d4a0071c99f522d23e052cfb185d381ea Mon Sep 17 00:00:00 2001
From: stefslon <stefslon@gmail.com>
Date: Thu, 8 Aug 2019 21:57:51 -0400
Subject: [PATCH] Add tileMargin option

---
 docs/config.rst       |  3 ++-
 src/serve_rendered.js | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/docs/config.rst b/docs/config.rst
index 6d6f99f..ae82cbf 100644
--- a/docs/config.rst
+++ b/docs/config.rst
@@ -27,7 +27,8 @@ Example::
       "maxSize": 2048,
       "pbfAlias": "pbf",
       "serveAllFonts": false,
-      "serveStaticMaps": true
+      "serveStaticMaps": true,
+      "tileMargin": 0
     },
     "styles": {
       "basic": {
diff --git a/src/serve_rendered.js b/src/serve_rendered.js
index 5a57f3f..ce8aba0 100644
--- a/src/serve_rendered.js
+++ b/src/serve_rendered.js
@@ -407,6 +407,13 @@ module.exports = function(options, repo, params, id, publicUrl, dataResolver) {
         params.width *= 2;
         params.height *= 2;
       }
+      
+      var tileMargin = Math.max(options.tileMargin || 0, 0);
+      if (z > 2 && tileMargin > 0) {
+        params.width += tileMargin * 2 * scale;
+        params.height += tileMargin * 2 * scale;
+      }
+
       renderer.render(params, function(err, data) {
         pool.release(renderer);
         if (err) {
@@ -421,6 +428,10 @@ module.exports = function(options, repo, params, id, publicUrl, dataResolver) {
             channels: 4
           }
         });
+        
+        if (z > 2 && tileMargin > 0) {
+            image.extract({ left: tileMargin * scale, top: tileMargin * scale, width: width * scale, height: height * scale });
+        }
 
         if (z == 0) {
           // HACK: when serving zoom 0, resize the 0 tile from 512 to 256