add a Center method to MbtilesMetadata

cmd/build/main.go

@@ -296,7 +296,7 @@ func main() {
 	log.Print("Finished processing tiles")
 
 	err = outputter.AssignSpatialMetadata(bounds, zooms[0], zooms[len(zooms)-1])
-	
+
 	if err != nil {
 		log.Printf("Wrote tiles but failed to assign spatial metadata, %v", err)
 	}

cmd/mbtiles-assign-metadata/main.go

@@ -1,57 +1,57 @@
 package main
 
 import (
-	"log"
 	"flag"
-
+	"log"
+
 	"github.com/paulmach/orb"
 	"github.com/paulmach/orb/maptile"
-	"github.com/tilezen/go-tilepacks/tilepack"	
+	"github.com/tilezen/go-tilepacks/tilepack"
 )
 
 func main() {
 
 	var verify bool
 
 	flag.BoolVar(&verify, "verify", false, "Verify that spatial metadata was written to each database")
-	
+
 	flag.Parse()
 
 	for _, path := range flag.Args() {
 
 		mbtilesReader, err := tilepack.NewMbtilesReader(path)
-		
+
 		if err != nil {
 			log.Fatalf("Couldn't read input mbtiles %s: %+v", path, err)
 		}
-		
+
 		var bounds *orb.Bound
 		minZoom := uint(20)
 		maxZoom := uint(0)
-		
+
 		err = mbtilesReader.VisitAllTiles(func(t maptile.Tile, data []byte) {
 
 			tb := t.Bound()
-			
+
 			if bounds == nil {
 				bounds = &tb
 			} else {
 				tb = bounds.Union(tb)
 				bounds = &tb
 			}
-						
+
 			minZoom = min(minZoom, uint(t.Z))
-			maxZoom = max(maxZoom, uint(t.Z))			
+			maxZoom = max(maxZoom, uint(t.Z))
 		})
-		
+
 		if err != nil {
 			log.Fatalf("Couldn't read tiles from %s: %+v", path, err)
 		}
 
 		mbtilesReader.Close()
-		
+
 		mbtilesWriter, err := tilepack.NewMbtilesOutputter(path, 0)
-		
+
 		if err != nil {
 			log.Fatalf("Couldn't read input mbtiles %s: %+v", path, err)
 		}
@@ -67,37 +67,42 @@ func main() {
 		if verify {
 
 			mbtilesReader, err := tilepack.NewMbtilesReader(path)
-			
+
 			if err != nil {
 				log.Fatalf("Couldn't read input mbtiles %s: %+v", path, err)
 			}
-			
+
 			metadata, err := mbtilesReader.Metadata()
-			
+
 			if err != nil {
 				log.Fatalf("Unable to read metadata for %s, %v", path, err)
 			}
-			
+
 			bounds, err := metadata.Bounds()
 
 			if err != nil {
 				log.Fatalf("Failed to derive bounds metadata after update")
 			}
 
+			center, err := metadata.Center()
+
+			if err != nil {
+				log.Fatalf("Failed to derive bounds metadata after update")
+			}
+
 			minZoom, err := metadata.MinZoom()
 
 			if err != nil {
 				log.Fatalf("Failed to derive min zoom metadata after update")
 			}
-			
+
 			maxZoom, err := metadata.MaxZoom()
-			
+
 			if err != nil {
 				log.Fatalf("Failed to derive max zoom metadata after update")
 			}
 
-			log.Printf("[%s] bounds: %v zoom: %d-%d\n", path, bounds, minZoom, maxZoom)
+			log.Printf("[%s] bounds: %v center: %v zoom: %d-%d\n", path, bounds, center, minZoom, maxZoom)
 		}
 	}
 }
-

tilepack/mbtiles_metadata.go

@@ -88,6 +88,38 @@ func (m *MbtilesMetadata) Bounds() (orb.Bound, error) {
 	return bounds, nil
 }
 
+func (m *MbtilesMetadata) Center() (orb.Point, error) {
+
+	var pt orb.Point
+
+	str_center, exists := m.Get("center")
+
+	if !exists {
+		return pt, fmt.Errorf("Metadata is missing center")
+	}
+
+	parts := strings.Split(str_center, ",")
+
+	if len(parts) != 2 {
+		return pt, fmt.Errorf("Invalid center metadata")
+	}
+
+	x, err := strconv.ParseFloat(parts[0], 64)
+
+	if err != nil {
+		return pt, fmt.Errorf("Failed to parse x, %w", err)
+	}
+
+	y, err := strconv.ParseFloat(parts[1], 64)
+
+	if err != nil {
+		return pt, fmt.Errorf("Failed to parse y, %w", err)
+	}
+
+	pt = orb.Point([2]float64{x, y})
+	return pt, nil
+}
+
 func (m *MbtilesMetadata) MinZoom() (uint, error) {
 
 	str_minzoom, exists := m.Get("minzoom")