Added FileNameComparator to sort the filenames in an ImageSequence into alphanumerical order so that it can handle the numerical ordering found in screenshot numbered sets of files

src/osgPresentation/SlideShowConstructor.cpp

@@ -857,6 +857,56 @@ osg::Geometry* SlideShowConstructor::createTexturedQuadGeometry(const osg::Vec3&
     return pictureQuad;
 }
 
+struct FileNameComparotor
+{
+    bool operator() (const std::string& lhs, const std::string& rhs) const
+    {
+        std::string::size_type size_lhs = lhs.size();
+        std::string::size_type size_rhs = rhs.size();
+        std::string::size_type pos_lhs = 0;
+        std::string::size_type pos_rhs = 0;
+        while(pos_lhs<size_lhs && pos_rhs<size_rhs)
+        {
+            char c_lhs = lhs[pos_rhs];
+            char c_rhs = rhs[pos_rhs];
+            bool numeric_lhs = lhs[pos_lhs]>='0' && lhs[pos_lhs]<='9';
+            bool numeric_rhs = rhs[pos_rhs]>='0' && rhs[pos_rhs]<='9';
+            if (numeric_lhs && numeric_rhs)
+            {
+                std::string::size_type start_lhs = pos_lhs;
+                ++pos_lhs;
+                while(pos_lhs<size_lhs && (lhs[pos_lhs]>='0' && lhs[pos_lhs]<='9')) ++pos_lhs;
+
+                std::string::size_type start_rhs = pos_rhs;
+                ++pos_rhs;
+                while(pos_rhs<size_rhs && (rhs[pos_rhs]>='0' && rhs[pos_rhs]<='9')) ++pos_rhs;
+
+                if (pos_lhs<pos_rhs) return true;
+                else if (pos_rhs<pos_lhs) return false;
+
+                while(start_lhs<pos_lhs && start_rhs<pos_rhs)
+                {
+                    if (lhs[start_lhs]<rhs[start_rhs]) return true;
+                    if (lhs[start_lhs]>rhs[start_rhs]) return false;
+                    ++start_lhs;
+                    ++start_rhs;
+                }                
+            }
+            else
+            {
+                if (c_lhs<c_rhs) return true;
+                else if (c_rhs<c_lhs) return false;
+
+                ++pos_lhs;
+                ++pos_rhs;
+            }
+        }
+
+        return pos_lhs<pos_rhs;
+    }
+};
+
+
 osg::Image* SlideShowConstructor::readImage(const std::string& filename, const ImageData& imageData)
 {
     osg::ref_ptr<osgDB::Options> options = _options;
@@ -932,7 +982,7 @@ osg::Image* SlideShowConstructor::readImage(const std::string& filename, const I
     else
     {
         // make sure images are in alphabetical order.
-        std::sort(filenames.begin(), filenames.end());
+        std::sort(filenames.begin(), filenames.end(), FileNameComparotor());
 
         osg::ref_ptr<osg::ImageSequence> imageSequence = new osg::ImageSequence;