MBTiles vector tile source (#740)

Support offline vector maps (MBTiles, MVT, gzipped pbf)

settings.gradle

@@ -3,6 +3,7 @@ include ':vtm'
 include ':vtm-android'
 include ':vtm-android-example'
 include ':vtm-android-gdx'
+include ':vtm-android-mvt'
 include ':vtm-app'
 include ':vtm-desktop'
 include ':vtm-desktop-lwjgl'

vtm-android-example/AndroidManifest.xml

@@ -79,7 +79,10 @@
             android:name=".MarkerOverlayActivity"
             android:configChanges="keyboardHidden|orientation|screenSize" />
         <activity
-            android:name=".MBTilesBitmapTileActivity"
+            android:name=".MBTilesBitmapActivity"
+            android:configChanges="keyboardHidden|orientation|screenSize" />
+        <activity
+            android:name=".MBTilesMvtActivity"
             android:configChanges="keyboardHidden|orientation|screenSize" />
         <activity
             android:name=".NextzenGeojsonActivity"

vtm-android-example/build.gradle

@@ -9,6 +9,7 @@ configurations.all {
 
 dependencies {
     implementation project(':vtm-android')
+    implementation project(':vtm-android-mvt')
     implementation project(':vtm-extras')
     implementation project(':vtm-http')
     implementation project(':vtm-jeo')

vtm-android-example/res/values/strings.xml

@@ -26,7 +26,7 @@
     <string name="search_value">void or value</string>
     <string name="now">Now</string>
     <string name="warning">Warning</string>
-    <string name="startup_message_mbtiles">To run this sample activity, you need any  MBTiles with filename test.mbtiles installed on storage.\n\nadb push file.mbtiles /sdcard/test.mbtiles</string>
+    <string name="startup_message_mbtiles">To run this sample activity, you need an MBTiles database installed on storage.\n\nadb push %s %s</string>
     <string name="exit">Exit</string>
 
 </resources>

vtm-android-example/src/org/oscim/android/test/MBTilesBitmapActivity.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2019 Andrea Antonello
  * Copyright 2019 devemux86
+ * Copyright 2019 Kostas Tzounopoulos
  *
  * This program is free software: you can redistribute it and/or modify it under the
  * terms of the GNU Lesser General Public License as published by the Free Software
@@ -19,6 +20,7 @@ import android.app.AlertDialog;
 import android.content.DialogInterface;
 import android.os.Bundle;
 import org.oscim.android.tiling.source.mbtiles.MBTilesBitmapTileSource;
+import org.oscim.android.tiling.source.mbtiles.MBTilesTileSource;
 import org.oscim.core.BoundingBox;
 import org.oscim.core.MapPosition;
 import org.oscim.core.Tile;
@@ -27,19 +29,19 @@ import org.oscim.layers.tile.bitmap.BitmapTileLayer;
 import java.io.File;
 
 /**
- * An example activity making use of MBTiles.
+ * An example activity making use of raster MBTiles.
  */
-public class MBTilesBitmapTileActivity extends BitmapTileActivity {
+public class MBTilesBitmapActivity extends BitmapTileActivity {
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
-        File file = new File(getExternalFilesDir(null), "test.mbtiles");
+        File file = new File(getExternalFilesDir(null), "raster.mbtiles");
         if (!file.exists()) {
             AlertDialog.Builder builder = new AlertDialog.Builder(this)
                     .setTitle(R.string.warning)
-                    .setMessage(R.string.startup_message_mbtiles)
+                    .setMessage(getResources().getString(R.string.startup_message_mbtiles, file.getName(), file.getAbsolutePath()))
                     .setPositiveButton(R.string.exit, new DialogInterface.OnClickListener() {
                         @Override
                         public void onClick(DialogInterface dialog, int which) {
@@ -50,7 +52,8 @@ public class MBTilesBitmapTileActivity extends BitmapTileActivity {
             return;
         }
 
-        MBTilesBitmapTileSource tileSource = new MBTilesBitmapTileSource(file.getAbsolutePath(), 128, null);
+        MBTilesTileSource tileSource = new MBTilesBitmapTileSource(file.getAbsolutePath(), 128, null);
+
         BitmapTileLayer bitmapLayer = new BitmapTileLayer(mMap, tileSource);
         mMap.layers().add(bitmapLayer);
 
@@ -58,7 +61,7 @@ public class MBTilesBitmapTileActivity extends BitmapTileActivity {
         MapPosition pos = new MapPosition();
         mMap.getMapPosition(pos);
         if (pos.x == 0.5 && pos.y == 0.5) {
-            BoundingBox bbox = tileSource.getBounds();
+            BoundingBox bbox = tileSource.getDataSource().getBounds();
             if (bbox != null) {
                 pos.setByBoundingBox(bbox, Tile.SIZE * 4, Tile.SIZE * 4);
                 mMap.setMapPosition(pos);

vtm-android-example/src/org/oscim/android/test/MBTilesMvtActivity.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2019 Andrea Antonello
+ * Copyright 2019 devemux86
+ * Copyright 2019 Kostas Tzounopoulos
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.oscim.android.test;
+
+import android.app.AlertDialog;
+import android.content.DialogInterface;
+import android.os.Bundle;
+import org.oscim.android.mvt.tiling.source.mbtiles.MBTilesMvtTileSource;
+import org.oscim.android.tiling.source.mbtiles.MBTilesTileSource;
+import org.oscim.android.tiling.source.mbtiles.MBTilesUnsupportedException;
+import org.oscim.core.BoundingBox;
+import org.oscim.core.MapPosition;
+import org.oscim.core.Tile;
+import org.oscim.layers.tile.buildings.BuildingLayer;
+import org.oscim.layers.tile.vector.VectorTileLayer;
+import org.oscim.layers.tile.vector.labeling.LabelLayer;
+import org.oscim.theme.VtmThemes;
+
+import java.io.File;
+
+/**
+ * An example activity making use of vector MBTiles.
+ */
+public class MBTilesMvtActivity extends MapActivity {
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        File file = new File(getExternalFilesDir(null), "vector.mbtiles");
+        if (!file.exists()) {
+            AlertDialog.Builder builder = new AlertDialog.Builder(this)
+                    .setTitle(R.string.warning)
+                    .setMessage(getResources().getString(R.string.startup_message_mbtiles, file.getName(), file.getAbsolutePath()))
+                    .setPositiveButton(R.string.exit, new DialogInterface.OnClickListener() {
+                        @Override
+                        public void onClick(DialogInterface dialog, int which) {
+                            finish();
+                        }
+                    });
+            builder.show();
+            return;
+        }
+
+        MBTilesTileSource tileSource;
+        try {
+            tileSource = new MBTilesMvtTileSource(file.getAbsolutePath(), "en");
+        } catch (MBTilesUnsupportedException e) {
+            AlertDialog.Builder builder = new AlertDialog.Builder(this)
+                    .setTitle(R.string.warning)
+                    .setMessage(e.getMessage())
+                    .setPositiveButton(R.string.exit, new DialogInterface.OnClickListener() {
+                        @Override
+                        public void onClick(DialogInterface dialog, int which) {
+                            finish();
+                        }
+                    });
+            builder.show();
+            return;
+        }
+
+        VectorTileLayer l = mMap.setBaseMap(tileSource);
+        mMap.setTheme(VtmThemes.OPENMAPTILES);
+
+        mMap.layers().add(new BuildingLayer(mMap, l));
+        mMap.layers().add(new LabelLayer(mMap, l));
+
+        /* set initial position on first run */
+        MapPosition pos = new MapPosition();
+        mMap.getMapPosition(pos);
+        if (pos.x == 0.5 && pos.y == 0.5) {
+            BoundingBox bbox = tileSource.getDataSource().getBounds();
+            if (bbox != null) {
+                pos.setByBoundingBox(bbox, Tile.SIZE * 4, Tile.SIZE * 4);
+                mMap.setMapPosition(pos);
+            }
+        }
+    }
+}

vtm-android-example/src/org/oscim/android/test/Samples.java

@@ -9,6 +9,7 @@
  * Copyright 2018 boldtrn
  * Copyright 2018-2019 Gustl22
  * Copyright 2019 Andrea Antonello
+ * Copyright 2019 Kostas Tzounopoulos
  *
  * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
  *
@@ -88,6 +89,7 @@ public class Samples extends Activity {
         linearLayout.addView(createLabel(null));
         linearLayout.addView(createButton(SimpleMapActivity.class));
         linearLayout.addView(createButton(MapsforgeActivity.class));
+        linearLayout.addView(createButton(MBTilesMvtActivity.class));
         linearLayout.addView(createButton(MapilionMvtActivity.class));
         /*linearLayout.addView(createButton(MapzenMvtActivity.class));
         linearLayout.addView(createButton(MapzenGeojsonActivity.class));
@@ -114,7 +116,7 @@ public class Samples extends Activity {
 
         linearLayout.addView(createLabel("Raster Maps"));
         linearLayout.addView(createButton(BitmapTileActivity.class));
-        linearLayout.addView(createButton(MBTilesBitmapTileActivity.class));
+        linearLayout.addView(createButton(MBTilesBitmapActivity.class));
 
         linearLayout.addView(createLabel("Overlays"));
         linearLayout.addView(createButton(MarkerOverlayActivity.class));

vtm-android-mvt/AndroidManifest.xml

@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<manifest package="org.oscim.android.mvt" />

vtm-android-mvt/build.gradle

@@ -0,0 +1,55 @@
+apply plugin: 'com.android.library'
+apply plugin: 'com.github.dcendents.android-maven'
+
+dependencies {
+    api project(':vtm-android')
+    api project(':vtm-mvt')
+}
+
+android {
+    compileSdkVersion androidCompileSdk()
+    buildToolsVersion "$androidBuildVersionTools"
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_7
+        targetCompatibility JavaVersion.VERSION_1_7
+    }
+
+    defaultConfig {
+        versionCode project.versionCode()
+        versionName project.versionName()
+        minSdkVersion androidMinSdk()
+        targetSdkVersion androidTargetSdk()
+    }
+
+    sourceSets {
+        main {
+            manifest.srcFile 'AndroidManifest.xml'
+            java.srcDirs = ['src']
+        }
+        debug.setRoot('build-types/debug')
+        release.setRoot('build-types/release')
+    }
+
+    lintOptions { abortOnError false }
+}
+
+android.libraryVariants.all { variant ->
+    def name = variant.buildType.name
+    if (name == "debug")
+        return
+
+    def jar = project.tasks.create "jar${name.capitalize()}", Jar
+    jar.dependsOn variant.javaCompileProvider
+    jar.exclude '**/BuildConfig.class'
+    jar.exclude '**/R.class'
+    jar.exclude '**/R$*.class'
+    jar.from variant.javaCompileProvider.get().destinationDir
+    artifacts.add('archives', jar)
+}
+
+if (project.hasProperty("SONATYPE_USERNAME")) {
+    afterEvaluate {
+        project.apply from: "${rootProject.projectDir}/deploy.gradle"
+    }
+}

vtm-android-mvt/src/org/oscim/android/mvt/tiling/source/mbtiles/MBTilesMvtTileDataSource.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2019 Kostas Tzounopoulos
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.oscim.android.mvt.tiling.source.mbtiles;
+
+import android.database.Cursor;
+import org.oscim.android.tiling.source.mbtiles.MBTilesTileDataSource;
+import org.oscim.android.tiling.source.mbtiles.MBTilesUnsupportedException;
+import org.oscim.core.MercatorProjection;
+import org.oscim.layers.tile.MapTile;
+import org.oscim.tiling.ITileDataSink;
+import org.oscim.tiling.OverzoomDataSink;
+import org.oscim.tiling.QueryResult;
+import org.oscim.tiling.source.mvt.MvtTileDecoder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.util.Collections;
+import java.util.List;
+import java.util.Locale;
+import java.util.zip.GZIPInputStream;
+
+/**
+ * A tile data source for MBTiles vector databases.
+ */
+public class MBTilesMvtTileDataSource extends MBTilesTileDataSource {
+
+    private static final Logger log = LoggerFactory.getLogger(MBTilesMvtTileDataSource.class);
+
+    private static final List<String> SUPPORTED_FORMATS = Collections.singletonList("pbf");
+    private static final String WHERE_FORMAT = "zoom_level=%d AND tile_column=%d AND tile_row=%d";
+
+    private final String mLanguage;
+
+    private final ThreadLocal<MvtTileDecoder> mThreadLocalDecoders = new ThreadLocal<MvtTileDecoder>() {
+        @Override
+        protected MvtTileDecoder initialValue() {
+            return new MvtTileDecoder(mLanguage);
+        }
+    };
+
+    /**
+     * Create a tile data source for MBTiles vector databases.
+     *
+     * @param path     the path to the MBTiles database.
+     * @param language the language to use when rendering the MBTiles.
+     */
+    public MBTilesMvtTileDataSource(String path, String language) {
+        super(path);
+        mLanguage = language != null ? language : "en";
+
+        try {
+            assertDatabaseFormat();
+        } catch (MBTilesUnsupportedException e) {
+            log.error("Invalid MBTiles database", e);
+        }
+    }
+
+    @Override
+    public void cancel() {
+        // do nothing
+    }
+
+    @Override
+    public void dispose() {
+        if (mDatabase != null && mDatabase.isOpen())
+            mDatabase.close();
+    }
+
+    @Override
+    public List<String> getSupportedFormats() {
+        return SUPPORTED_FORMATS;
+    }
+
+    private MapTile mapTile(Cursor cursor) {
+        int tileX = cursor.getInt(cursor.getColumnIndexOrThrow("tile_column"));
+        int tileY = cursor.getInt(cursor.getColumnIndexOrThrow("tile_row"));
+        int zoomLevel = cursor.getInt(cursor.getColumnIndexOrThrow("zoom_level"));
+        long tmsTileY = MercatorProjection.tileYToTMS(tileY, (byte) zoomLevel);
+        return new MapTile(tileX, (int) tmsTileY, zoomLevel);
+    }
+
+    /**
+     * Overzoom on the DB layer: generate a query for all tiles with lower zoomLevel than the one requested.
+     */
+    private String overzoomQuery(MapTile tile) {
+        long tmsTileY = MercatorProjection.tileYToTMS(tile.tileY, tile.zoomLevel);
+        StringBuilder sb = new StringBuilder();
+        sb.append("(");
+        for (int zoomLevel = tile.zoomLevel - 1; zoomLevel > 0; zoomLevel--) {
+            int diff = tile.zoomLevel - zoomLevel;
+            sb.append(String.format(Locale.US, WHERE_FORMAT, zoomLevel, tile.tileX >> diff, tmsTileY >> diff));
+            if (zoomLevel > 1) // Not the last iteration
+                sb.append(") OR (");
+        }
+        sb.append(")");
+        return String.format(SELECT_TILES_FORMAT, sb.toString());
+    }
+
+    @Override
+    public void query(MapTile requestTile, ITileDataSink requestDataSink) {
+        Cursor cursor = null;
+        ITileDataSink responseDataSink = requestDataSink;
+        try {
+            long tmsTileY = MercatorProjection.tileYToTMS(requestTile.tileY, requestTile.zoomLevel);
+            cursor = mDatabase.rawQuery(String.format(SELECT_TILES_FORMAT, String.format(Locale.US, WHERE_FORMAT, requestTile.zoomLevel, requestTile.tileX, tmsTileY)), null);
+
+            if (cursor.getCount() == 0) {
+                cursor.close();
+                cursor = mDatabase.rawQuery(overzoomQuery(requestTile), null);
+            }
+
+            if (cursor.moveToFirst()) {
+                byte[] bytes = cursor.getBlob(cursor.getColumnIndexOrThrow("tile_data"));
+
+                MapTile responseTile = mapTile(cursor);
+                if (requestTile.zoomLevel != responseTile.zoomLevel)
+                    responseDataSink = new OverzoomDataSink(requestDataSink, responseTile, requestTile);
+
+                boolean success = mThreadLocalDecoders.get().decode(responseTile, responseDataSink, new GZIPInputStream(new ByteArrayInputStream(bytes)));
+                responseDataSink.completed(success ? QueryResult.SUCCESS : QueryResult.FAILED);
+            } else
+                responseDataSink.completed(QueryResult.TILE_NOT_FOUND);
+        } catch (IOException e) {
+            responseDataSink.completed(QueryResult.FAILED);
+        } finally {
+            if (cursor != null)
+                cursor.close();
+        }
+    }
+}

vtm-android-mvt/src/org/oscim/android/mvt/tiling/source/mbtiles/MBTilesMvtTileSource.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2019 Kostas Tzounopoulos
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.oscim.android.mvt.tiling.source.mbtiles;
+
+import org.oscim.android.tiling.source.mbtiles.MBTilesTileSource;
+
+/**
+ * A tile source for MBTiles vector databases.
+ */
+public class MBTilesMvtTileSource extends MBTilesTileSource {
+
+    /**
+     * Create a tile source for MBTiles vector databases.
+     *
+     * @param path the path to the MBTiles database.
+     */
+    public MBTilesMvtTileSource(String path) {
+        this(path, null);
+    }
+
+    /**
+     * Create a tile source for MBTiles vector databases.
+     *
+     * @param path     the path to the MBTiles database.
+     * @param language the language to use when rendering the MBTiles.
+     */
+    public MBTilesMvtTileSource(String path, String language) {
+        super(new MBTilesMvtTileDataSource(path, language));
+    }
+}

vtm-android/src/org/oscim/android/tiling/source/mbtiles/MBTilesBitmapTileDataSource.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2019 Andrea Antonello
  * Copyright 2019 devemux86
+ * Copyright 2019 Kostas Tzounopoulos
  *
  * This program is free software: you can redistribute it and/or modify it under the
  * terms of the GNU Lesser General Public License as published by the Free Software
@@ -16,144 +17,70 @@
 package org.oscim.android.tiling.source.mbtiles;
 
 import android.database.Cursor;
-import android.database.sqlite.SQLiteDatabase;
 import android.graphics.BitmapFactory;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
 import org.oscim.backend.CanvasAdapter;
 import org.oscim.backend.canvas.Bitmap;
-import org.oscim.core.BoundingBox;
 import org.oscim.core.MercatorProjection;
 import org.oscim.layers.tile.MapTile;
-import org.oscim.map.Viewport;
 import org.oscim.tiling.ITileDataSink;
-import org.oscim.tiling.ITileDataSource;
 import org.oscim.tiling.QueryResult;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
-import java.util.HashMap;
+import java.util.Arrays;
-import java.util.Map;
+import java.util.List;
 
 /**
  * A tile data source for MBTiles raster databases.
  */
-public class MBTilesBitmapTileDataSource implements ITileDataSource {
+public class MBTilesBitmapTileDataSource extends MBTilesTileDataSource {
 
     private static final Logger log = LoggerFactory.getLogger(MBTilesBitmapTileDataSource.class);
 
-    private static final String TABLE_TILES = "tiles";
+    private static final List<String> SUPPORTED_FORMATS = Arrays.asList("png", "jpg", "jpeg");
-    private static final String COL_TILES_ZOOM_LEVEL = "zoom_level";
-    private static final String COL_TILES_TILE_COLUMN = "tile_column";
-    private static final String COL_TILES_TILE_ROW = "tile_row";
-    private static final String COL_TILES_TILE_DATA = "tile_data";
-    private static final String SELECT_TILES = "SELECT " + COL_TILES_TILE_DATA + " from " + TABLE_TILES + " where "
-            + COL_TILES_ZOOM_LEVEL + "=? AND " + COL_TILES_TILE_COLUMN + "=? AND " + COL_TILES_TILE_ROW + "=?";
-
-    private static final String TABLE_METADATA = "metadata";
-    private static final String COL_METADATA_NAME = "name";
-    private static final String COL_METADATA_VALUE = "value";
-    private static final String SELECT_METADATA = "select " + COL_METADATA_NAME + "," + COL_METADATA_VALUE + " from "
-            + TABLE_METADATA;
 
     private final Integer mAlpha;
-    private final SQLiteDatabase mDatabase;
-    private Map<String, String> mMetadata;
     private final Integer mTransparentColor;
 
     /**
-     * Create a MBTiles tile data source.
+     * Create a tile data source for MBTiles raster databases.
      *
      * @param path             the path to the MBTiles database.
      * @param alpha            an optional alpha value [0-255] to make the tiles transparent.
      * @param transparentColor an optional color that will be made transparent in the bitmap.
      */
-    MBTilesBitmapTileDataSource(String path, Integer alpha, Integer transparentColor) {
+    public MBTilesBitmapTileDataSource(String path, Integer alpha, Integer transparentColor) {
-        mDatabase = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
+        super(path);
         mAlpha = alpha;
         mTransparentColor = transparentColor;
+
+        try {
+            assertDatabaseFormat();
+        } catch (MBTilesUnsupportedException e) {
+            log.error("Invalid MBTiles database", e);
+        }
     }
 
     @Override
     public void cancel() {
-        mDatabase.close();
+        if (mDatabase != null && mDatabase.isOpen())
+            mDatabase.close();
     }
 
     @Override
     public void dispose() {
-        mDatabase.close();
+        if (mDatabase != null && mDatabase.isOpen())
+            mDatabase.close();
     }
 
-    String getAttribution() {
+    @Override
-        return getMetadata().get("attribution");
+    public List<String> getSupportedFormats() {
-    }
+        return SUPPORTED_FORMATS;
-
-    BoundingBox getBounds() {
-        String bounds = getMetadata().get("bounds");
-        if (bounds != null) {
-            String[] split = bounds.split(",");
-            double w = Double.parseDouble(split[0]);
-            double s = Double.parseDouble(split[1]);
-            double e = Double.parseDouble(split[2]);
-            double n = Double.parseDouble(split[3]);
-            return new BoundingBox(s, w, n, e);
-        }
-        return null;
-    }
-
-    public String getDescription() {
-        return getMetadata().get("description");
-    }
-
-    /**
-     * @return the image format (jpg, png)
-     */
-    public String getFormat() {
-        return getMetadata().get("format");
-    }
-
-    int getMaxZoom() {
-        String maxZoom = getMetadata().get("maxzoom");
-        if (maxZoom != null)
-            return Integer.parseInt(maxZoom);
-        return Viewport.MAX_ZOOM_LEVEL;
-    }
-
-    private Map<String, String> getMetadata() {
-        if (mMetadata == null) {
-            mMetadata = new HashMap<>();
-            Cursor cursor = null;
-            try {
-                cursor = mDatabase.rawQuery(SELECT_METADATA, null);
-                while (cursor.moveToNext()) {
-                    String key = cursor.getString(0);
-                    String value = cursor.getString(1);
-                    mMetadata.put(key, value);
-                }
-            } finally {
-                if (cursor != null)
-                    cursor.close();
-            }
-        }
-        return mMetadata;
-    }
-
-    int getMinZoom() {
-        String minZoom = getMetadata().get("minzoom");
-        if (minZoom != null)
-            return Integer.parseInt(minZoom);
-        return Viewport.MIN_ZOOM_LEVEL;
-    }
-
-    String getName() {
-        return getMetadata().get("name");
-    }
-
-    public String getVersion() {
-        return getMetadata().get("version");
     }
 
     private static android.graphics.Bitmap processAlpha(android.graphics.Bitmap bitmap, int alpha) {
@@ -216,9 +143,9 @@ public class MBTilesBitmapTileDataSource implements ITileDataSource {
         Cursor cursor = null;
         try {
             long tmsTileY = MercatorProjection.tileYToTMS(tileY, zoomLevel);
-            cursor = mDatabase.rawQuery(SELECT_TILES, new String[]{String.valueOf(zoomLevel), String.valueOf(tileX), String.valueOf(tmsTileY)});
+            cursor = mDatabase.rawQuery(String.format(MBTilesTileDataSource.SELECT_TILES_FORMAT, MBTilesTileDataSource.WHERE_FORMAT), new String[]{String.valueOf(zoomLevel), String.valueOf(tileX), String.valueOf(tmsTileY)});
             if (cursor.moveToFirst())
-                return cursor.getBlob(0);
+                return cursor.getBlob(cursor.getColumnIndexOrThrow("tile_data"));
         } finally {
             if (cursor != null)
                 cursor.close();

vtm-android/src/org/oscim/android/tiling/source/mbtiles/MBTilesBitmapTileSource.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2019 Andrea Antonello
  * Copyright 2019 devemux86
+ * Copyright 2019 Kostas Tzounopoulos
  *
  * This program is free software: you can redistribute it and/or modify it under the
  * terms of the GNU Lesser General Public License as published by the Free Software
@@ -15,19 +16,13 @@
  */
 package org.oscim.android.tiling.source.mbtiles;
 
-import org.oscim.core.BoundingBox;
-import org.oscim.tiling.ITileDataSource;
-import org.oscim.tiling.TileSource;
-
 /**
  * A tile source for MBTiles raster databases.
  */
-public class MBTilesBitmapTileSource extends TileSource {
+public class MBTilesBitmapTileSource extends MBTilesTileSource {
-
-    private final MBTilesBitmapTileDataSource mTileDataSource;
 
     /**
-     * Create a MBTiles tile source.
+     * Create a tile source for MBTiles raster databases.
      *
      * @param path the path to the MBTiles database.
      */
@@ -36,64 +31,13 @@ public class MBTilesBitmapTileSource extends TileSource {
     }
 
     /**
-     * Create a MBTiles tile source.
+     * Create a tile source for MBTiles raster databases.
      *
      * @param path             the path to the MBTiles database.
      * @param alpha            an optional alpha value [0-255] to make the tiles transparent.
      * @param transparentColor an optional color that will be made transparent in the bitmap.
      */
     public MBTilesBitmapTileSource(String path, Integer alpha, Integer transparentColor) {
-        mTileDataSource = new MBTilesBitmapTileDataSource(path, alpha, transparentColor);
+        super(new MBTilesBitmapTileDataSource(path, alpha, transparentColor));
-    }
-
-    @Override
-    public void close() {
-        mTileDataSource.dispose();
-    }
-
-
-    public String getAttribution() {
-        return mTileDataSource.getAttribution();
-    }
-
-    public BoundingBox getBounds() {
-        return mTileDataSource.getBounds();
-    }
-
-    @Override
-    public ITileDataSource getDataSource() {
-        return mTileDataSource;
-    }
-
-    public String getDescription() {
-        return mTileDataSource.getDescription();
-    }
-
-    /**
-     * @return the image format (jpg, png)
-     */
-    public String getFormat() {
-        return mTileDataSource.getFormat();
-    }
-
-    public int getMaxZoom() {
-        return mTileDataSource.getMaxZoom();
-    }
-
-    public int getMinZoom() {
-        return mTileDataSource.getMinZoom();
-    }
-
-    public String getName() {
-        return mTileDataSource.getName();
-    }
-
-    public String getVersion() {
-        return mTileDataSource.getVersion();
-    }
-
-    @Override
-    public OpenResult open() {
-        return OpenResult.SUCCESS;
     }
 }

vtm-android/src/org/oscim/android/tiling/source/mbtiles/MBTilesTileDataSource.java

@@ -0,0 +1,154 @@
+/*
+ * Copyright 2019 Andrea Antonello
+ * Copyright 2019 devemux86
+ * Copyright 2019 Kostas Tzounopoulos
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.oscim.android.tiling.source.mbtiles;
+
+import android.database.Cursor;
+import android.database.sqlite.SQLiteDatabase;
+import android.text.TextUtils;
+import org.oscim.core.BoundingBox;
+import org.oscim.core.MapPosition;
+import org.oscim.map.Viewport;
+import org.oscim.tiling.ITileDataSource;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A tile data source for MBTiles databases.
+ */
+public abstract class MBTilesTileDataSource implements ITileDataSource {
+
+    private static final String SELECT_METADATA = "SELECT name, value FROM metadata";
+    protected static final String SELECT_TILES_FORMAT =
+            "SELECT zoom_level, tile_column, tile_row, tile_data " +
+                    "FROM tiles " +
+                    "WHERE %s " +
+                    "ORDER BY zoom_level DESC " +
+                    "LIMIT 1";
+    static final String WHERE_FORMAT = "zoom_level=? AND tile_column=? AND tile_row=?";
+
+    protected final SQLiteDatabase mDatabase;
+    private Map<String, String> mMetadata;
+
+    public MBTilesTileDataSource(String path) {
+        mDatabase = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
+    }
+
+    protected void assertDatabaseFormat() {
+        String format = getFormat();
+
+        if (format == null)
+            throw new RuntimeException("'metadata.format' field was not found. Is this an MBTiles database?");
+
+        List<String> supportedFormats = getSupportedFormats();
+        if (!supportedFormats.contains(format))
+            throw new MBTilesUnsupportedException(String.format("Unsupported MBTiles 'metadata.format: %s'. Supported format(s) are: %s", format, TextUtils.join(", ", supportedFormats)));
+    }
+
+    public String getAttribution() {
+        return getMetadata().get("attribution");
+    }
+
+    public BoundingBox getBounds() {
+        String bounds = getMetadata().get("bounds");
+        if (bounds == null)
+            return null;
+        String[] split = bounds.split(",");
+        double w = Double.parseDouble(split[0]);
+        double s = Double.parseDouble(split[1]);
+        double e = Double.parseDouble(split[2]);
+        double n = Double.parseDouble(split[3]);
+        return new BoundingBox(s, w, n, e);
+    }
+
+    public MapPosition getCenter() {
+        String center = getMetadata().get("center");
+        if (center == null)
+            return null;
+        String[] split = center.split(",");
+        double latitude = Double.parseDouble(split[1]);
+        double longitude = Double.parseDouble(split[0]);
+        int zoomLevel = Integer.parseInt(split[2]);
+        return new MapPosition(latitude, longitude, 1 << zoomLevel);
+    }
+
+    public String getDescription() {
+        return getMetadata().get("description");
+    }
+
+    public String getFormat() {
+        return getMetadata().get("format");
+    }
+
+    public String getId() {
+        return getMetadata().get("id");
+    }
+
+    public String getJson() {
+        return getMetadata().get("json");
+    }
+
+    public int getMaxZoom() {
+        String maxZoom = getMetadata().get("maxzoom");
+        return maxZoom != null ? Integer.parseInt(maxZoom) : Viewport.MAX_ZOOM_LEVEL;
+    }
+
+    private Map<String, String> getMetadata() {
+        if (mMetadata == null) {
+            mMetadata = new HashMap<>();
+            Cursor cursor = null;
+            try {
+                cursor = mDatabase.rawQuery(SELECT_METADATA, null);
+                while (cursor.moveToNext()) {
+                    String key = cursor.getString(0);
+                    String value = cursor.getString(1);
+                    mMetadata.put(key, value);
+                }
+            } finally {
+                if (cursor != null)
+                    cursor.close();
+            }
+        }
+        return mMetadata;
+    }
+
+    public int getMinZoom() {
+        String minZoom = getMetadata().get("minzoom");
+        return minZoom != null ? Integer.parseInt(minZoom) : Viewport.MIN_ZOOM_LEVEL;
+    }
+
+    public Long getMTime() {
+        String mTime = getMetadata().get("mtime");
+        return mTime != null ? Long.parseLong(mTime) : null;
+    }
+
+    public String getName() {
+        return getMetadata().get("name");
+    }
+
+    public Integer getPixelScale() {
+        String pixelScale = getMetadata().get("pixel_scale");
+        return pixelScale != null ? Integer.parseInt(pixelScale) : null;
+    }
+
+    abstract public List<String> getSupportedFormats();
+
+    public String getVersion() {
+        return getMetadata().get("version");
+    }
+}

vtm-android/src/org/oscim/android/tiling/source/mbtiles/MBTilesTileSource.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2019 Andrea Antonello
+ * Copyright 2019 devemux86
+ * Copyright 2019 Kostas Tzounopoulos
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.oscim.android.tiling.source.mbtiles;
+
+import org.oscim.tiling.TileSource;
+
+/**
+ * A tile source for MBTiles databases.
+ */
+public abstract class MBTilesTileSource extends TileSource {
+
+    private final MBTilesTileDataSource mTileDataSource;
+
+    public MBTilesTileSource(MBTilesTileDataSource tileDataSource) {
+        mTileDataSource = tileDataSource;
+    }
+
+    @Override
+    public void close() {
+        getDataSource().dispose();
+    }
+
+    @Override
+    public MBTilesTileDataSource getDataSource() {
+        return mTileDataSource;
+    }
+
+    @Override
+    public OpenResult open() {
+        return OpenResult.SUCCESS;
+    }
+}

vtm-android/src/org/oscim/android/tiling/source/mbtiles/MBTilesUnsupportedException.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2019 Kostas Tzounopoulos
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.oscim.android.tiling.source.mbtiles;
+
+public class MBTilesUnsupportedException extends RuntimeException {
+    public MBTilesUnsupportedException(String message) {
+        super(message);
+    }
+}

vtm/src/org/oscim/tiling/OverzoomDataSink.java

@@ -22,7 +22,7 @@ import org.oscim.core.Tile;
 import org.oscim.utils.geom.TileClipper;
 import org.oscim.utils.geom.TileSeparator;
 
-class OverzoomDataSink implements ITileDataSink {
+public class OverzoomDataSink implements ITileDataSink {
 
     private final ITileDataSink sink;
 
@@ -30,7 +30,7 @@ class OverzoomDataSink implements ITileDataSink {
     private final TileSeparator separator;
     private final float dx, dy, scale;
 
-    OverzoomDataSink(ITileDataSink sink, Tile overzoomTile, Tile tile) {
+    public OverzoomDataSink(ITileDataSink sink, Tile overzoomTile, Tile tile) {
         this.sink = sink;
 
         int diff = tile.zoomLevel - overzoomTile.zoomLevel;