Access MBTiles file with correct Y axis

geofabrik · Nov 9, 2023 · 55eac73 · 55eac73
1 parent 1d2270f
commit 55eac73
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Showing 4 changed files with 23 additions and 17 deletions.
diff --git a/src/mbtiles_vector_featureset.cpp b/src/mbtiles_vector_featureset.cpp
@@ -42,6 +42,11 @@ mapnik::feature_ptr mbtiles_vector_featureset::next()
     return mapnik::feature_ptr();
 }
 
+int mbtiles_vector_featureset::convert_y(const int y) const
+{
+    return (1 << zoom_) - 1 - y;
+}
+
 bool mbtiles_vector_featureset::next_tile()
 {
     ++x_;
@@ -56,7 +61,7 @@ bool mbtiles_vector_featureset::next_tile()
 
 bool mbtiles_vector_featureset::open_tile()
 {
-    std::string sql = (boost::format("SELECT tile_data FROM tiles WHERE zoom_level = %1% AND tile_column = %2% AND tile_row = %3%") % zoom_ % x_ % y_).str();
+    std::string sql = (boost::format("SELECT tile_data FROM tiles WHERE zoom_level = %1% AND tile_column = %2% AND tile_row = %3%") % zoom_ % x_ % convert_y(y_)).str();
     std::shared_ptr<sqlite_resultset> result (database_->execute_query(sql));
     int size = 0;
     char const* blob = nullptr;

diff --git a/src/mbtiles_vector_featureset.hpp b/src/mbtiles_vector_featureset.hpp
@@ -55,6 +55,10 @@ class mbtiles_vector_featureset : public mapnik::Featureset
     int x_ = 0;
     /// y index of the currently accessed tile
     int y_ = 0;
+    /**
+     * Transform Y index (tile_row) from z/x/y to TMS schema.
+     */
+    int convert_y(const int y) const;
 
     bool next_tile();
     bool open_tile();

diff --git a/src/mvt_io.cpp b/src/mvt_io.cpp
@@ -159,7 +159,7 @@ mapnik::feature_ptr mvt_layer::next_feature()
     return mapnik::feature_ptr();
 }
 
-void mvt_io::read_layer(protozero::pbf_reader& pbf_layer)
+bool mvt_io::read_layer(protozero::pbf_reader& pbf_layer)
 //void mvt_io::read_layer(protozero::pbf_message<mvt_message::layer>& pbf_layer)
 {
     layer_.reset(new mvt_layer(x_, y_, zoom_));
@@ -252,6 +252,8 @@ void mvt_io::read_layer(protozero::pbf_reader& pbf_layer)
         }
     }
     layer_->finish_reading();
+    std::cerr << '\n';
+    return !ignore_layer;
 }
 
 mapnik::feature_ptr mvt_io::next()
@@ -270,23 +272,15 @@ mvt_io::mvt_io(std::string&& data, const uint32_t x, const uint32_t y, const uin
         zoom_(zoom),
         layer_name_(layer_name)
 {
-    while (reader_.next())
-    {
-        switch (reader_.tag_and_type()) {
-        case tag_and_type(static_cast<uint32_t>(mvt_message::tile::layer), protozero::pbf_wire_type::length_delimited): {
-            std::cerr << "got layer\n";
-            const auto data_view(reader_.get_view());
+    while (reader_.next(static_cast<uint32_t>(mvt_message::tile::layer))) {
+        std::cerr << "got layer\n";
+        const auto data_view(reader_.get_view());
 //            protozero::pbf_message<mvt_message::layer> msg_layer(reader_.get_message());
-            protozero::pbf_reader msg_layer(data_view);
-            read_layer(msg_layer);
-//            read_layers();
-            break;
-        }
-        default:
-            std::cerr << "got tag " << reader_.tag() << " type " << static_cast<uint32_t>(reader_.wire_type()) << '\n';
-            reader_.skip();
+        protozero::pbf_reader msg_layer(data_view);
+        if (read_layer(msg_layer)) {
             break;
         }
+//            read_layers();
     }
 }
 
diff --git a/src/mvt_io.hpp b/src/mvt_io.hpp
@@ -121,7 +121,10 @@ class mvt_io
     const int tile_extent_ = -1;
     std::unique_ptr<mvt_layer> layer_;
 
-    void read_layer(protozero::pbf_reader& l);
+    /**
+     * Read a layer from PBF. Returns true if requested layer was parsed.
+     */
+    bool read_layer(protozero::pbf_reader& l);
 //    void read_layer(protozero::pbf_message<mvt_message::layer>& l);
 //    void read_layers();