Bitmap: get png encoded data implementation

vtm-android-gdx/src/org/oscim/android/canvas/AndroidBitmap.java

@@ -21,6 +21,7 @@ import android.graphics.BitmapFactory;
 import android.opengl.GLES20;
 import android.opengl.GLUtils;
 
+import java.io.ByteArrayOutputStream;
 import java.io.InputStream;
 
 import static android.graphics.Bitmap.Config.ARGB_8888;
@@ -43,6 +44,13 @@ public class AndroidBitmap implements org.oscim.backend.canvas.Bitmap {
         return mBitmap != null;
     }
 
+    @Override
+    public byte[] getPngEncodedData() {
+        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+        this.mBitmap.compress(Bitmap.CompressFormat.PNG, 0, outputStream);
+        return outputStream.toByteArray();
+    }
+
     /**
      * @param format ignored always ARGB8888
      */