From 2e4476d43b67229d25121aa29517900b09b49b76 Mon Sep 17 00:00:00 2001
From: Pirmin Kalberer <pirmin.kalberer@gmail.com>
Date: Fri, 23 Aug 2024 16:26:16 +0200
Subject: [PATCH] Use floor for coordinate transformation (#229)

This solves artifacts from asymmetric rounding around zero. See
https://github.com/t-rex-tileserver/t-rex/pull/319
---
 geozero/src/mvt/mvt_writer.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/geozero/src/mvt/mvt_writer.rs b/geozero/src/mvt/mvt_writer.rs
index dc032392..ffffff06 100644
--- a/geozero/src/mvt/mvt_writer.rs
+++ b/geozero/src/mvt/mvt_writer.rs
@@ -74,8 +74,8 @@ impl GeomProcessor for MvtWriter {
         if !last_ring_coord {
             let (x, y) = if self.extent != 0 {
                 // scale to tile coordinate space
-                let x = ((x_coord - self.left) * self.x_multiplier) as i32;
-                let y = ((y_coord - self.bottom) * self.y_multiplier) as i32;
+                let x = ((x_coord - self.left) * self.x_multiplier).floor() as i32;
+                let y = ((y_coord - self.bottom) * self.y_multiplier).floor() as i32;
                 // Y is stored as reversed
                 (x, self.extent.saturating_sub(y))
             } else {