Render themes: tag transform (#587)

resources/rendertheme.xsd

@@ -301,11 +301,24 @@
         <xs:attribute name="id" type="xs:string" use="required" />
     </xs:complexType>
 
+    <!-- tag-transform element -->
+    <xs:complexType name="tag-transform">
+        <xs:attribute name="k" type="xs:string" use="required" />
+        <xs:attribute name="v" type="xs:string" use="optional" />
+        <xs:attribute name="k-match" type="xs:string" use="required" />
+        <xs:attribute name="v-match" type="xs:string" use="optional" />
+    </xs:complexType>
+
     <!-- rendertheme element -->
     <xs:complexType name="rendertheme">
         <xs:sequence maxOccurs="1" minOccurs="0">
             <xs:element name="stylemenu" maxOccurs="1" minOccurs="0" type="tns:stylemenu" />
 
+            <!-- tag definitions -->
+            <xs:choice maxOccurs="unbounded" minOccurs="0">
+                <xs:element name="tag-transform" type="tns:tag-transform" />
+            </xs:choice>
+
             <!-- style definitions -->
             <xs:sequence maxOccurs="256" minOccurs="0">
                 <xs:choice maxOccurs="unbounded" minOccurs="0">

vtm-jeo/src/org/oscim/theme/carto/RenderTheme.java

@@ -251,6 +251,20 @@ public class RenderTheme implements IRenderTheme {
     public void scaleTextSize(float scaleFactor) {
     }
 
+    @Override
+    public String transformKey(String key) {
+        return null;
+    }
+
+    @Override
+    public Tag transformTag(Tag tag) {
+        return null;
+    }
+
+    @Override
+    public void updateStyles() {
+    }
+
     public static void main(String[] args) {
         RenderTheme t = new RenderTheme();
 
@@ -261,11 +275,4 @@ public class RenderTheme implements IRenderTheme {
         t.matchElement(GeometryType.POLY, e.tags, 16);
         t.matchElement(GeometryType.POLY, e.tags, 15);
     }
-
-    @Override
-    public void updateStyles() {
-        // TODO Auto-generated method stub
-
-    }
-
 }

vtm-playground/src/org/oscim/test/DebugTheme.java

@@ -2,6 +2,7 @@ package org.oscim.test;
 
 import org.oscim.backend.canvas.Color;
 import org.oscim.core.GeometryBuffer.GeometryType;
+import org.oscim.core.Tag;
 import org.oscim.core.TagSet;
 import org.oscim.theme.IRenderTheme;
 import org.oscim.theme.styles.AreaStyle;
@@ -46,6 +47,16 @@ public class DebugTheme implements IRenderTheme {
     public void scaleTextSize(float scaleFactor) {
     }
 
+    @Override
+    public String transformKey(String key) {
+        return null;
+    }
+
+    @Override
+    public Tag transformTag(Tag tag) {
+        return null;
+    }
+
     @Override
     public void updateStyles() {
     }

vtm-themes/resources/assets/vtm/mapzen.xml

@@ -3,6 +3,17 @@
     version="1" xmlns="http://opensciencemap.org/rendertheme"
     xsi:schemaLocation="http://opensciencemap.org/rendertheme https://raw.githubusercontent.com/mapsforge/vtm/master/resources/rendertheme.xsd">
 
+    <!--<tag-transform k="kind" v="building" k-match="building" v-match="yes" />-->
+    <!--<tag-transform k="kind" v="building_part" k-match="building:part" v-match="yes" />-->
+    <tag-transform k="root_id" k-match="ref" />
+
+    <tag-transform k="roof_color" k-match="roof:colour" />
+    <tag-transform k="roof_direction" k-match="roof:direction" />
+    <tag-transform k="roof_height" k-match="roof:height" />
+    <tag-transform k="roof_material" k-match="roof:material" />
+    <tag-transform k="roof_orientation" k-match="roof:orientation" />
+    <tag-transform k="roof_shape" k-match="roof:shape" />
+
     <!-- base style for fixed width lines -->
     <style-line cap="butt" fix="true" id="fix" width="1.0" />
 

vtm-themes/resources/assets/vtm/openmaptiles.xml

@@ -3,6 +3,11 @@
     version="1" xmlns="http://opensciencemap.org/rendertheme"
     xsi:schemaLocation="http://opensciencemap.org/rendertheme https://raw.githubusercontent.com/mapsforge/vtm/master/resources/rendertheme.xsd">
 
+    <tag-transform k="render_height" k-match="height" />
+    <tag-transform k="render_min_height" k-match="min_height" />
+    <!--<tag-transform k="layer" v="building" k-match="building" v-match="yes" />-->
+    <!--<tag-transform k="layer" v="building:part" k-match="building:part" v-match="yes" />-->
+
     <!--###### TEXT styles ######-->
 
     <!--default label-->

vtm/src/org/oscim/core/MapElement.java

@@ -19,6 +19,8 @@
  */
 package org.oscim.core;
 
+import org.oscim.theme.IRenderTheme;
+
 /**
  * The MapElement class is a reusable container for a geometry
  * with tags.
@@ -63,10 +65,9 @@ public class MapElement extends GeometryBuffer {
     /**
      * @return height in meters, if present
      */
-    public Float getHeight() {
+    public Float getHeight(IRenderTheme theme) {
-        String v = tags.getValue(Tag.KEY_HEIGHT);
+        String res = theme.transformKey(Tag.KEY_HEIGHT);
-        if (v == null)
+        String v = tags.getValue(res != null ? res : Tag.KEY_HEIGHT);
-            v = tags.getValue("render_height"); // OpenMapTiles
         if (v != null)
             return Float.parseFloat(v);
         return null;
@@ -75,22 +76,21 @@ public class MapElement extends GeometryBuffer {
     /**
      * @return minimum height in meters, if present
      */
-    public Float getMinHeight() {
+    public Float getMinHeight(IRenderTheme theme) {
-        String v = tags.getValue(Tag.KEY_MIN_HEIGHT);
+        String res = theme.transformKey(Tag.KEY_MIN_HEIGHT);
-        if (v == null)
+        String v = tags.getValue(res != null ? res : Tag.KEY_MIN_HEIGHT);
-            v = tags.getValue("render_min_height"); // OpenMapTiles
         if (v != null)
             return Float.parseFloat(v);
         return null;
     }
 
-    public boolean isBuilding() {
+    public boolean isBuilding() { // TODO from themes (with overzoom ref)
         return tags.containsKey(Tag.KEY_BUILDING)
                 || "building".equals(tags.getValue("kind")) // Mapzen
                 || "building".equals(tags.getValue("layer")); // OpenMapTiles
     }
 
-    public boolean isBuildingPart() {
+    public boolean isBuildingPart() { // TODO from themes (with overzoom ref)
         return tags.containsKey(Tag.KEY_BUILDING_PART)
                 || "building_part".equals(tags.getValue("kind")) // Mapzen
                 || "building:part".equals(tags.getValue("layer")); // OpenMapTiles

vtm/src/org/oscim/core/Tag.java

@@ -65,9 +65,9 @@ public class Tag {
     public static final String KEY_BUILDING_MATERIAL = "building:material";
     public static final String KEY_BUILDING_MIN_LEVEL = "building:min_level";
     public static final String KEY_BUILDING_PART = "building:part";
-    public static final String KEY_COLOR = "colour";
+    //public static final String KEY_COLOR = "colour";
     public static final String KEY_HEIGHT = "height";
-    public static final String KEY_MATERIAL = "material";
+    //public static final String KEY_MATERIAL = "material";
     public static final String KEY_MIN_HEIGHT = "min_height";
     public static final String KEY_ROOF = "roof";
     public static final String KEY_ROOF_ANGLE = "roof:angle";

vtm/src/org/oscim/layers/tile/buildings/BuildingLayer.java

@@ -31,6 +31,7 @@ import org.oscim.renderer.OffscreenRenderer;
 import org.oscim.renderer.OffscreenRenderer.Mode;
 import org.oscim.renderer.bucket.ExtrusionBuckets;
 import org.oscim.renderer.bucket.RenderBuckets;
+import org.oscim.theme.IRenderTheme;
 import org.oscim.theme.styles.ExtrusionStyle;
 import org.oscim.theme.styles.RenderStyle;
 
@@ -66,6 +67,8 @@ public class BuildingLayer extends Layer implements TileLoaderThemeHook, ZoomLim
 
     private final ZoomLimiter mZoomLimiter;
 
+    protected final IRenderTheme mRenderTheme;
+
     class BuildingElement {
         MapElement element;
         ExtrusionStyle style;
@@ -103,6 +106,8 @@ public class BuildingLayer extends Layer implements TileLoaderThemeHook, ZoomLim
         mRenderer = new BuildingRenderer(tileLayer.tileRenderer(), mZoomLimiter, mesh, TRANSLUCENT);
         if (POST_AA)
             mRenderer = new OffscreenRenderer(Mode.SSAO_FXAA, mRenderer);
+
+        mRenderTheme = tileLayer.getTheme();
     }
 
     @Override
@@ -160,22 +165,22 @@ public class BuildingLayer extends Layer implements TileLoaderThemeHook, ZoomLim
         int height = 0; // cm
         int minHeight = 0; // cm
 
-        Float f = element.getHeight();
+        Float f = element.getHeight(mRenderTheme);
         if (f != null)
             height = (int) (f * 100);
         else {
             // #TagFromTheme: generalize level/height tags
-            String v = element.tags.getValue(Tag.KEY_BUILDING_LEVELS);
+            String v = getValue(element, Tag.KEY_BUILDING_LEVELS);
             if (v != null)
                 height = (int) (Float.parseFloat(v) * BUILDING_LEVEL_HEIGHT);
         }
 
-        f = element.getMinHeight();
+        f = element.getMinHeight(mRenderTheme);
         if (f != null)
             minHeight = (int) (f * 100);
         else {
             // #TagFromTheme: level/height tags
-            String v = element.tags.getValue(Tag.KEY_BUILDING_MIN_LEVEL);
+            String v = getValue(element, Tag.KEY_BUILDING_MIN_LEVEL);
             if (v != null)
                 minHeight = (int) (Float.parseFloat(v) * BUILDING_LEVEL_HEIGHT);
         }
@@ -202,15 +207,14 @@ public class BuildingLayer extends Layer implements TileLoaderThemeHook, ZoomLim
             if (!partBuilding.element.isBuildingPart())
                 continue;
 
-            String refId = partBuilding.element.tags.getValue(Tag.KEY_REF); // #TagFromTheme
+            String refId = getValue(partBuilding.element, Tag.KEY_REF);
-            refId = refId == null ? partBuilding.element.tags.getValue("root_id") : refId; // Mapzen
             if (refId == null)
                 continue;
 
             // Search buildings which inherit parts
             for (BuildingElement rootBuilding : tileBuildings) {
                 if (rootBuilding.element.isBuildingPart()
-                        || !(refId.equals(rootBuilding.element.tags.getValue(Tag.KEY_ID))))
+                        || !(refId.equals(getValue(rootBuilding.element, Tag.KEY_ID))))
                     continue;
 
                 rootBuildings.add(rootBuilding);
@@ -239,6 +243,15 @@ public class BuildingLayer extends Layer implements TileLoaderThemeHook, ZoomLim
         return ebs;
     }
 
+    protected String getKeyOrDefault(String key) {
+        String res = mRenderTheme.transformKey(key);
+        return res != null ? res : key;
+    }
+
+    protected String getValue(MapElement element, String key) {
+        return element.tags.getValue(getKeyOrDefault(key));
+    }
+
     @Override
     public void complete(MapTile tile, boolean success) {
         if (success) {

vtm/src/org/oscim/layers/tile/buildings/S3DBLayer.java

@@ -101,12 +101,12 @@ public class S3DBLayer extends BuildingLayer {
         int roofHeight = 0;
 
         // Get roof height
-        String v = element.tags.getValue(Tag.KEY_ROOF_HEIGHT);
+        String v = getValue(element, Tag.KEY_ROOF_HEIGHT);
         if (v != null) {
             roofHeight = (int) (Float.parseFloat(v) * 100);
-        } else if ((v = element.tags.getValue(Tag.KEY_ROOF_LEVELS)) != null) {
+        } else if ((v = getValue(element, Tag.KEY_ROOF_LEVELS)) != null) {
             roofHeight = (int) (Float.parseFloat(v) * BUILDING_LEVEL_HEIGHT);
-        } else if ((v = element.tags.getValue(Tag.KEY_ROOF_ANGLE)) != null) {
+        } else if ((v = getValue(element, Tag.KEY_ROOF_ANGLE)) != null) {
             Box bb = null;
             for (int k = 0; k < element.index[0]; k += 2) {
                 float p1 = element.points[k];
@@ -122,17 +122,17 @@ public class S3DBLayer extends BuildingLayer {
                 // Angle is simplified, 40 is an estimated constant
                 roofHeight = (int) ((Float.parseFloat(v) / 45.f) * (minSize * 40));
             }
-        } else if ((v = element.tags.getValue(Tag.KEY_ROOF_SHAPE)) != null && !v.equals(Tag.VALUE_FLAT)) {
+        } else if ((v = getValue(element, Tag.KEY_ROOF_SHAPE)) != null && !v.equals(Tag.VALUE_FLAT)) {
             roofHeight = (2 * BUILDING_LEVEL_HEIGHT);
         }
 
         // Get building height
-        v = element.tags.getValue(Tag.KEY_HEIGHT);
+        v = getValue(element, Tag.KEY_HEIGHT);
         if (v != null) {
             maxHeight = (int) (Float.parseFloat(v) * 100);
         } else {
             // #TagFromTheme: generalize level/height tags
-            if ((v = element.tags.getValue(Tag.KEY_BUILDING_LEVELS)) != null) {
+            if ((v = getValue(element, Tag.KEY_BUILDING_LEVELS)) != null) {
                 maxHeight = (int) (Float.parseFloat(v) * BUILDING_LEVEL_HEIGHT);
                 maxHeight += roofHeight;
             }
@@ -140,22 +140,22 @@ public class S3DBLayer extends BuildingLayer {
         if (maxHeight == 0)
             maxHeight = extrusion.defaultHeight * 100;
 
-        v = element.tags.getValue(Tag.KEY_MIN_HEIGHT);
+        v = getValue(element, Tag.KEY_MIN_HEIGHT);
         if (v != null)
             minHeight = (int) (Float.parseFloat(v) * 100);
         else {
             // #TagFromTheme: level/height tags
-            if ((v = element.tags.getValue(Tag.KEY_BUILDING_MIN_LEVEL)) != null)
+            if ((v = getValue(element, Tag.KEY_BUILDING_MIN_LEVEL)) != null)
                 minHeight = (int) (Float.parseFloat(v) * BUILDING_LEVEL_HEIGHT);
         }
 
         // Get building color
         Integer bColor = null;
         if (mColored) {
-            if (element.tags.containsKey(Tag.KEY_BUILDING_COLOR)) {
+            if ((v = getValue(element, Tag.KEY_BUILDING_COLOR)) != null) {
-                bColor = S3DBUtils.getColor(element.tags.getValue(Tag.KEY_BUILDING_COLOR), false, false);
+                bColor = S3DBUtils.getColor(v, false, false);
-            } else if (element.tags.containsKey(Tag.KEY_BUILDING_MATERIAL)) {
+            } else if ((v = getValue(element, Tag.KEY_BUILDING_MATERIAL)) != null) {
-                bColor = S3DBUtils.getMaterialColor(element.tags.getValue(Tag.KEY_BUILDING_MATERIAL), false);
+                bColor = S3DBUtils.getMaterialColor(v, false);
             }
         }
 
@@ -190,25 +190,32 @@ public class S3DBLayer extends BuildingLayer {
             if (!partBuilding.element.isBuildingPart())
                 continue;
 
-            TagSet partTags = partBuilding.element.tags;
+            String refId = getValue(partBuilding.element, Tag.KEY_REF);
-            String refId = partTags.getValue(Tag.KEY_REF); // #TagFromTheme
-            refId = refId == null ? partTags.getValue("root_id") : refId; // Mapzen
             if (refId == null)
                 continue;
 
+            TagSet partTags = partBuilding.element.tags;
+
             // Search buildings which inherit parts
             for (BuildingElement rootBuilding : tileBuildings) {
                 if (rootBuilding.element.isBuildingPart()
                         || !(refId.equals(rootBuilding.element.tags.getValue(Tag.KEY_ID))))
                     continue;
 
+                if ((getValue(rootBuilding.element, Tag.KEY_ROOF_SHAPE) != null)
+                        && (getValue(partBuilding.element, Tag.KEY_ROOF_SHAPE) == null)) {
+                    partBuilding.element.tags.add(rootBuilding.element.tags.get(getKeyOrDefault(Tag.KEY_ROOF_SHAPE)));
+                }
+
                 if (mColored) {
                     TagSet rootTags = rootBuilding.element.tags;
+
                     for (int i = 0; i < rootTags.size(); i++) {
                         Tag rTag = rootTags.get(i);
-                        if ((rTag.key.equals(Tag.KEY_COLOR) && !partTags.containsKey(Tag.KEY_MATERIAL)
+                        if ((rTag.key.equals(getKeyOrDefault(Tag.KEY_BUILDING_COLOR))
-                                || rTag.key.equals(Tag.KEY_ROOF_COLOR) && !partTags.containsKey(Tag.KEY_ROOF_MATERIAL)
+                                && !partTags.containsKey(getKeyOrDefault(Tag.KEY_BUILDING_MATERIAL))
-                                || rTag.key.equals(Tag.KEY_ROOF_SHAPE))
+                                || rTag.key.equals(getKeyOrDefault(Tag.KEY_ROOF_COLOR))
+                                && !partTags.containsKey(getKeyOrDefault(Tag.KEY_ROOF_MATERIAL)))
                                 && !partTags.containsKey(rTag.key)) {
                             partTags.add(rTag);
                         }
@@ -243,22 +250,22 @@ public class S3DBLayer extends BuildingLayer {
         String v;
 
         if (mColored) {
-            v = element.tags.getValue(Tag.KEY_ROOF_COLOR);
+            v = getValue(element, Tag.KEY_ROOF_COLOR);
             if (v != null)
                 roofColor = S3DBUtils.getColor(v, true, false);
-            else if ((v = element.tags.getValue(Tag.KEY_ROOF_MATERIAL)) != null)
+            else if ((v = getValue(element, Tag.KEY_ROOF_MATERIAL)) != null)
                 roofColor = S3DBUtils.getMaterialColor(v, true);
         }
 
         boolean roofOrientationAcross = false;
-        if ((v = element.tags.getValue(Tag.KEY_ROOF_ORIENTATION)) != null) {
+        if ((v = getValue(element, Tag.KEY_ROOF_ORIENTATION)) != null) {
             if (v.equals(Tag.VALUE_ACROSS)) {
                 roofOrientationAcross = true;
             }
         }
 
         // Calc roof shape
-        v = element.tags.getValue(Tag.KEY_ROOF_SHAPE);
+        v = getValue(element, Tag.KEY_ROOF_SHAPE);
         if (v == null) {
             v = Tag.VALUE_FLAT;
         }

vtm/src/org/oscim/theme/IRenderTheme.java

@@ -2,6 +2,7 @@
  * Copyright 2010, 2011, 2012 mapsforge.org
  * Copyright 2013 Hannes Janetzek
  * Copyright 2017 devemux86
+ * Copyright 2018 Gustl22
  *
  * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
  *
@@ -19,6 +20,7 @@
 package org.oscim.theme;
 
 import org.oscim.core.GeometryBuffer.GeometryType;
+import org.oscim.core.Tag;
 import org.oscim.core.TagSet;
 import org.oscim.theme.styles.RenderStyle;
 
@@ -63,6 +65,16 @@ public interface IRenderTheme {
      */
     void scaleTextSize(float scaleFactor);
 
+    /**
+     * @return the transformed tag key of this RenderTheme.
+     */
+    String transformKey(String key);
+
+    /**
+     * @return the transformed tag of this RenderTheme.
+     */
+    Tag transformTag(Tag tag);
+
     class ThemeException extends IllegalArgumentException {
         public ThemeException(String string) {
             super(string);

vtm/src/org/oscim/theme/RenderTheme.java

@@ -2,6 +2,7 @@
  * Copyright 2014 Hannes Janetzek
  * Copyright 2017 Longri
  * Copyright 2017 devemux86
+ * Copyright 2018 Gustl22
  *
  * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
  *
@@ -19,6 +20,7 @@
 package org.oscim.theme;
 
 import org.oscim.core.GeometryBuffer.GeometryType;
+import org.oscim.core.Tag;
 import org.oscim.core.TagSet;
 import org.oscim.theme.rule.Rule;
 import org.oscim.theme.rule.Rule.Element;
@@ -31,6 +33,7 @@ import org.slf4j.LoggerFactory;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 
 public class RenderTheme implements IRenderTheme {
     static final Logger log = LoggerFactory.getLogger(RenderTheme.class);
@@ -44,6 +47,9 @@ public class RenderTheme implements IRenderTheme {
     private final Rule[] mRules;
     private final boolean mMapsforgeTheme;
 
+    private final Map<String, String> mTransformKeyMap;
+    private final Map<Tag, Tag> mTransformTagMap;
+
     class RenderStyleCache {
         final int matchType;
         final LRUCache<MatchingCacheKey, RenderStyleItem> cache;
@@ -79,7 +85,17 @@ public class RenderTheme implements IRenderTheme {
         this(mapBackground, baseTextSize, rules, levels, false);
     }
 
+    public RenderTheme(int mapBackground, float baseTextSize, Rule[] rules, int levels,
+                       Map<String, String> transformKeyMap, Map<Tag, Tag> transformTagMap) {
+        this(mapBackground, baseTextSize, rules, levels, transformKeyMap, transformTagMap, false);
+    }
+
     public RenderTheme(int mapBackground, float baseTextSize, Rule[] rules, int levels, boolean mapsforgeTheme) {
+        this(mapBackground, baseTextSize, rules, levels, null, null, mapsforgeTheme);
+    }
+
+    public RenderTheme(int mapBackground, float baseTextSize, Rule[] rules, int levels,
+                       Map<String, String> transformKeyMap, Map<Tag, Tag> transformTagMap, boolean mapsforgeTheme) {
         if (rules == null)
             throw new IllegalArgumentException("rules missing");
 
@@ -89,6 +105,9 @@ public class RenderTheme implements IRenderTheme {
         mRules = rules;
         mMapsforgeTheme = mapsforgeTheme;
 
+        mTransformKeyMap = transformKeyMap;
+        mTransformTagMap = transformTagMap;
+
         mStyleCache = new RenderStyleCache[3];
         mStyleCache[0] = new RenderStyleCache(Element.NODE);
         mStyleCache[1] = new RenderStyleCache(Element.LINE);
@@ -272,6 +291,20 @@ public class RenderTheme implements IRenderTheme {
             rule.scaleTextSize(scaleFactor * mBaseTextSize);
     }
 
+    @Override
+    public String transformKey(String key) {
+        if (mTransformKeyMap != null)
+            return mTransformKeyMap.get(key);
+        return null;
+    }
+
+    @Override
+    public Tag transformTag(Tag tag) {
+        if (mTransformTagMap != null)
+            return mTransformTagMap.get(tag);
+        return null;
+    }
+
     @Override
     public void updateStyles() {
         for (Rule rule : mRules)

vtm/src/org/oscim/theme/XmlThemeBuilder.java

@@ -4,6 +4,7 @@
  * Copyright 2016-2018 devemux86
  * Copyright 2016-2017 Longri
  * Copyright 2016 Andrey Novikov
+ * Copyright 2018 Gustl22
  *
  * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
  *
@@ -64,6 +65,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Set;
 import java.util.Stack;
 
@@ -168,6 +170,9 @@ public class XmlThemeBuilder extends DefaultHandler {
     private XmlRenderThemeStyleLayer mCurrentLayer;
     private XmlRenderThemeStyleMenu mRenderThemeStyleMenu;
 
+    private Map<String, String> mTransformKeyMap = new HashMap<>();
+    private Map<Tag, Tag> mTransformTagMap = new HashMap<>();
+
     public XmlThemeBuilder(ThemeFile theme) {
         this(theme, null);
     }
@@ -202,7 +207,7 @@ public class XmlThemeBuilder extends DefaultHandler {
     }
 
     RenderTheme createTheme(Rule[] rules) {
-        return new RenderTheme(mMapBackground, mTextScale, rules, mLevels, mMapsforgeTheme);
+        return new RenderTheme(mMapBackground, mTextScale, rules, mLevels, mTransformKeyMap, mTransformTagMap, mMapsforgeTheme);
     }
 
     @Override
@@ -369,6 +374,10 @@ public class XmlThemeBuilder extends DefaultHandler {
                 mRenderThemeStyleMenu = new XmlRenderThemeStyleMenu(getStringAttribute(attributes, "id"),
                         getStringAttribute(attributes, "defaultlang"), getStringAttribute(attributes, "defaultvalue"));
 
+            } else if ("tag-transform".equals(localName)) {
+                checkState(qName, Element.RENDERING_STYLE);
+                tagTransform(localName, attributes);
+
             } else {
                 log.error("unknown element: {}", localName);
                 throw new SAXException("unknown element: " + localName);
@@ -1239,6 +1248,44 @@ public class XmlThemeBuilder extends DefaultHandler {
         return dashIntervals;
     }
 
+    private void tagTransform(String localName, Attributes attributes) {
+        String k, v, matchKey, matchValue;
+        k = v = matchKey = matchValue = null;
+
+        for (int i = 0; i < attributes.getLength(); i++) {
+            String name = attributes.getLocalName(i);
+            String value = attributes.getValue(i);
+
+            switch (name) {
+                case "k":
+                    k = value;
+                    break;
+                case "v":
+                    v = value;
+                    break;
+                case "k-match":
+                    matchKey = value;
+                    break;
+                case "v-match":
+                    matchValue = value;
+                    break;
+                default:
+                    logUnknownAttribute(localName, name, value, i);
+            }
+        }
+
+        if (k == null || k.isEmpty() || matchKey == null || matchKey.isEmpty()) {
+            log.debug("empty key in element " + localName);
+            return;
+        }
+
+        if (v == null && matchValue == null) {
+            mTransformKeyMap.put(matchKey, k);
+        } else {
+            mTransformTagMap.put(new Tag(matchKey, matchValue), new Tag(k, v));
+        }
+    }
+
     private static void validateNonNegative(String name, float value) {
         if (value < 0)
             throw new ThemeException(name + " must not be negative: "