Reverse y for scaled MVT tiles

georust · Jul 27, 2023 · f44e832 · f44e832
1 parent 1271e35
commit f44e832
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Showing 2 changed files with 25 additions and 18 deletions.
diff --git a/geozero/src/mvt/mvt_writer.rs b/geozero/src/mvt/mvt_writer.rs
@@ -11,7 +11,7 @@ use super::mvt_error::MvtError;
 /// Generator for MVT geometry type.
 pub struct MvtWriter {
     pub(crate) feature: tile::Feature,
-    tile_size: f64,
+    tile_size: Option<f64>,
     // Tile extent
     left: f64,
     bottom: f64,
@@ -35,7 +35,7 @@ enum LineState {
 impl MvtWriter {
     pub fn new(tile_size: u32, left: f64, bottom: f64, right: f64, top: f64) -> MvtWriter {
         MvtWriter {
-            tile_size: tile_size as f64,
+            tile_size: Some(tile_size as f64),
             left,
             bottom,
             right,
@@ -62,11 +62,11 @@ impl Default for MvtWriter {
     fn default() -> Self {
         Self {
             feature: tile::Feature::default(),
-            tile_size: 512.0,
+            tile_size: None,
             left: 0.0,
             bottom: 0.0,
-            right: 512.0,
-            top: 512.0,
+            right: 0.0,
+            top: 0.0,
             last_x: 0,
             last_y: 0,
             line_state: LineState::None,
@@ -76,7 +76,7 @@ impl Default for MvtWriter {
 }
 
 impl GeomProcessor for MvtWriter {
-    fn xy(&mut self, x: f64, y: f64, idx: usize) -> Result<()> {
+    fn xy(&mut self, x_coord: f64, y_coord: f64, idx: usize) -> Result<()> {
         // Omit last coord of ring (emit ClosePath instead)
         let last_ring_coord = if let LineState::Ring(size) = self.line_state {
             idx == size - 1
@@ -85,8 +85,17 @@ impl GeomProcessor for MvtWriter {
         };
 
         if !last_ring_coord {
-            let x = ((x - self.left) * self.tile_size / (self.right - self.left)) as i32;
-            let y = ((y - self.bottom) * self.tile_size / (self.top - self.bottom)) as i32;
+            let x: i32;
+            let mut y: i32;
+            if let Some(tile_size) = self.tile_size {
+                x = ((x_coord - self.left) * tile_size / (self.right - self.left)) as i32;
+                y = ((y_coord - self.bottom) * tile_size / (self.top - self.bottom)) as i32;
+                y = (tile_size as i32).saturating_sub(y); // reverse_y only?
+            } else {
+                // unscaled
+                x = x_coord as i32;
+                y = y_coord as i32;
+            }
             self.feature
                 .geometry
                 .push(ParameterInteger::from(x.saturating_sub(self.last_x)));
@@ -396,7 +405,6 @@ mod test_mvt {
 #[cfg(feature = "with-geojson")]
 mod test {
     use super::*;
-    use crate::api::GeozeroGeometry;
     use crate::geojson::conversion::ToJson;
     use crate::geojson::GeoJson;
     use crate::ToMvt;
@@ -487,15 +495,14 @@ mod test {
     fn geo_to_mvt() -> Result<()> {
         let geo: geo_types::Geometry<f64> = geo_types::Point::new(960000.0, 6002729.0).into();
         let mvt = geo.to_mvt(256, 958826.08, 5987771.04, 978393.96, 6007338.92)?;
-        assert_eq!(mvt.geometry, [9, 30, 390]);
+        assert_eq!(mvt.geometry, [9, 30, 122]);
         let geojson = mvt.to_json()?;
-
         assert_eq!(
             serde_json::from_str::<serde_json::Value>(&geojson).unwrap(),
             json!({
                 "type": "Point",
-                "coordinates": [15,195]
-            }) // ??!! reverse_y: y = tile_size.saturating_sub(y) -> [15,61]
+                "coordinates": [15,61]
+            }) // without reverse_y: [15,195]
         );
         Ok(())
     }

diff --git a/geozero/tests/mvt.rs b/geozero/tests/mvt.rs
@@ -1,7 +1,7 @@
-use geozero::mvt::{Message, MvtWriter, Tile};
+use geozero::mvt::{Message, Tile};
 use geozero::{
     ColumnValue, CoordDimensions, FeatureProcessor, GeomProcessor, GeozeroDatasource,
-    GeozeroGeometry, PropertyProcessor, ToJson, ToMvt,
+    PropertyProcessor, ToJson, ToMvt,
 };
 use serde_json::json;
 use std::env;
@@ -21,15 +21,15 @@ fn geo_to_mvt() {
     let mvt = geo
         .to_mvt(256, 958826.08, 5987771.04, 978393.96, 6007338.92)
         .unwrap();
-    assert_eq!(mvt.geometry, [9, 30, 390]);
+    assert_eq!(mvt.geometry, [9, 30, 122]);
     let geojson = mvt.to_json().unwrap();
 
     assert_eq!(
         serde_json::from_str::<serde_json::Value>(&geojson).unwrap(),
         json!({
             "type": "Point",
-            "coordinates": [15,195]
-        }) // ??!! reverse_y: y = tile_size.saturating_sub(y) -> [15,61]
+            "coordinates": [15,61]
+        })
     );
 }