From Brad Christiansen, "Attached is a fix which implements the lazy loading of optional layers (if requested) in the new osgb/osgt formats."

include/osgDB/InputStream

@@ -136,7 +136,7 @@ public:
     // Global reading functions
     osg::Array* readArray();
     osg::PrimitiveSet* readPrimitiveSet();
-    osg::Image* readImage();
+    osg::Image* readImage(bool readFromExternal=true);
     osg::Object* readObject( osg::Object* existingObj=0 );
     osg::Object* readObjectFields( const std::string& className, osg::Object* existingObj=0);
     

src/osgDB/InputStream.cpp

@@ -476,8 +476,9 @@ osg::PrimitiveSet* InputStream::readPrimitiveSet()
     return primitive.release();
 }
 
-osg::Image* InputStream::readImage()
+osg::Image* InputStream::readImage(bool readFromExternal) 
 {
+
     std::string className="osg::Image";
     unsigned int id = 0;
 
@@ -497,7 +498,7 @@ osg::Image* InputStream::readImage()
     if ( getException() ) return NULL;
 
     osg::ref_ptr<osg::Image> image = NULL;
-    bool readFromExternal = true;
+    
     switch ( decision )
     {
     case IMAGE_INLINE_DATA:

src/osgWrappers/serializers/osgTerrain/ImageLayer.cpp

@@ -3,10 +3,49 @@
 #include <osgDB/InputStream>
 #include <osgDB/OutputStream>
 
+#include <osgTerrain/TerrainTile>
+
+
+static bool checkImage( const osgTerrain::ImageLayer& im )
+{ return im.getImage() != NULL; }
+
+static bool readImage( osgDB::InputStream& is, osgTerrain::ImageLayer& il )
+{      
+            
+    if(!is.isBinary()) is >> osgDB::BEGIN_BRACKET;    
+
+    bool deferExternalLayerLoading = osgTerrain::TerrainTile::getTileLoadedCallback().valid() ? 
+            osgTerrain::TerrainTile::getTileLoadedCallback()->deferExternalLayerLoading() : false;          
+
+    
+    osg::ref_ptr<osg::Image> image = is.readImage(!deferExternalLayerLoading);
+    if (image.valid())
+    {
+        if(image->valid()) 
+        {
+            il.setImage(image.get());          
+        } 
+    } 
+    if(!is.isBinary()) is >> osgDB::END_BRACKET;        
+
+   return true;
+}
+
+static bool writeImage( osgDB::OutputStream& os, const osgTerrain::ImageLayer& il )
+{ 
+    const osg::Image* image = il.getImage();   
+
+    if(!os.isBinary()) os << osgDB::BEGIN_BRACKET << std::endl;                
+    os.writeImage(image);
+    if(!os.isBinary()) os << osgDB::END_BRACKET << std::endl; 
+          
+    return true;  
+}
+
 REGISTER_OBJECT_WRAPPER( osgTerrain_ImageLayer,
                          new osgTerrain::ImageLayer,
                          osgTerrain::ImageLayer,
                          "osg::Object osgTerrain::Layer osgTerrain::ImageLayer" )
-{
-    ADD_IMAGE_SERIALIZER( Image, osg::Image, NULL );  // _image
+{    
+   ADD_USER_SERIALIZER( Image );   
 }