From Ralf Habacker, "The appended patch fixes this issue by adding a virtual method named supportedFeatures() to the class ReaderWriter, which could be overriden by a specific plugin to adjust the set of features.

Single features are implemented as bits asother enums in ReaderWriter class already does, so that combinations are possible and fast comparison operations are possible

By default all features are enabled.

I have added this virtual method to the dot plugin to get an idea how to use these features.

With this patch osgconv --formats shows an additional line 'features' for each plugin"

src/osgDB/ReaderWriter.cpp

@@ -60,3 +60,40 @@ void ReaderWriter::supportsOption(const std::string& fmt, const std::string& des
 {
     _supportedOptions[fmt] = description;
 }
+
+ReaderWriter::Features ReaderWriter::supportedFeatures() const
+{
+    Features features = FEATURE_ALL;
+    return features;
+}
+
+ReaderWriter::FeatureList ReaderWriter::featureAsString(ReaderWriter::Features feature)
+{
+    typedef struct {
+        ReaderWriter::Features feature;
+        const char *s;
+    } FeatureStringList;
+
+    FeatureStringList list[] = { 
+        { FEATURE_READ_OBJECT, "readObject" },
+        { FEATURE_READ_IMAGE,  "readImage" },        
+        { FEATURE_READ_HEIGHT_FIELD, "readHeightField" },
+        { FEATURE_READ_NODE, "readNode" },          
+        { FEATURE_READ_SHADER, "readShader" },        
+        { FEATURE_WRITE_OBJECT, "writeObject" },
+        { FEATURE_WRITE_IMAGE, "writeImage" },        
+        { FEATURE_WRITE_HEIGHT_FIELD, "writeHeightField" },
+        { FEATURE_WRITE_NODE, "writeNode" },         
+        { FEATURE_WRITE_SHADER, "writeShader" },
+        { FEATURE_NONE,0 }
+    };
+
+    FeatureList result; 
+    
+    for(FeatureStringList *p=list; p->feature != 0; p++)
+    {
+        if ((feature & p->feature) != 0)
+            result.push_back(p->s);
+    }
+    return result;
+}