diff --git a/include/mapnik/image_filter.hpp b/include/mapnik/image_filter.hpp
index 4f09f2c2e..1ed44b0df 100644
--- a/include/mapnik/image_filter.hpp
+++ b/include/mapnik/image_filter.hpp
@@ -449,11 +449,11 @@ void apply_filter(Src & src, hsla const& op)
                     double s2 = tint.s0 + (s * (tint.s1 - tint.s0));
                     double l2 = tint.l0 + (l * (tint.l1 - tint.l0));
                     if (h2 > 1) h2 = 1;
-                    if (h2 < 0) h2 = 0;
+                    else if (h2 < 0) h2 = 0;
                     if (s2 > 1) s2 = 1;
-                    if (s2 < 0) s2 = 0;
+                    else if (s2 < 0) s2 = 0;
                     if (l2 > 1) l2 = 1;
-                    if (l2 < 0) l2 = 0;
+                    else if (l2 < 0) l2 = 0;
                     hsl2rgb(h2,s2,l2,r,g,b);
                     // premultiply
                     // we only work with premultiplied source,
diff --git a/include/mapnik/image_filter_grammar.hpp b/include/mapnik/image_filter_grammar.hpp
index 054cd856e..823b21b93 100644
--- a/include/mapnik/image_filter_grammar.hpp
+++ b/include/mapnik/image_filter_grammar.hpp
@@ -39,7 +39,10 @@ struct image_filter_grammar :
 {
     image_filter_grammar();
     qi::rule<Iterator, ContType(), qi::ascii::space_type> start;
-    qi::rule<Iterator, ContType(), qi::locals<int,int>, qi::ascii::space_type> filter;
+    qi::rule<Iterator, ContType(), qi::ascii::space_type> filter;
+    qi::rule<Iterator, qi::locals<int,int>, void(ContType&), qi::ascii::space_type> agg_blur_filter;
+    qi::rule<Iterator, qi::locals<std::string>, void(ContType&), qi::ascii::space_type> hsla_filter;
+    qi::rule<Iterator, std::string(), qi::ascii::space_type> string_arg;
     qi::uint_parser< unsigned, 10, 1, 3 > radius_;
 };
 
diff --git a/include/mapnik/image_filter_types.hpp b/include/mapnik/image_filter_types.hpp
index 9504d441d..cf49ed0d6 100644
--- a/include/mapnik/image_filter_types.hpp
+++ b/include/mapnik/image_filter_types.hpp
@@ -30,7 +30,6 @@
 #include <boost/variant/variant_fwd.hpp>
 
 // stl
-#include <iostream>
 #include <vector>
 #include <ostream>
 #include <iterator>  // for std::back_insert_iterator
@@ -71,7 +70,8 @@ typedef boost::variant<filter::blur,
                        filter::sobel,
                        filter::x_gradient,
                        filter::y_gradient,
-                       filter::invert> filter_type;
+                       filter::invert,
+                       filter::hsla> filter_type;
 
 inline std::ostream& operator<< (std::ostream& os, blur)
 {
diff --git a/include/mapnik/util/hsl.hpp b/include/mapnik/util/hsl.hpp
index 715b8f72c..3c8c62e2f 100644
--- a/include/mapnik/util/hsl.hpp
+++ b/include/mapnik/util/hsl.hpp
@@ -2,7 +2,7 @@
  *
  * This file is part of Mapnik (c++ mapping toolkit)
  *
- * Copyright (C) 2012 Artem Pavlenko
+ * Copyright (C) 2013 Artem Pavlenko
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
diff --git a/src/image_filter_grammar.cpp b/src/image_filter_grammar.cpp
index 1601b2904..80becb931 100644
--- a/src/image_filter_grammar.cpp
+++ b/src/image_filter_grammar.cpp
@@ -44,8 +44,11 @@ image_filter_grammar<Iterator,ContType>::image_filter_grammar()
     using qi::_1;
     using qi::_a;
     using qi::_b;
+    using qi::_r1;
     using qi::eps;
     using qi::char_;
+    using qi::lexeme;
+    using boost::spirit::ascii::string;
     using phoenix::push_back;
     using phoenix::construct;
 
@@ -75,15 +78,26 @@ image_filter_grammar<Iterator,ContType>::image_filter_grammar()
         |
         lit("y-gradient")[push_back(_val,construct<mapnik::filter::y_gradient>())]
         |
-        (lit("agg-stack-blur")[_a = 1, _b = 1]
-         >> -( lit('(') >> radius_[_a = _1]
-               >> lit(',')
-               >> radius_[_b = _1]
-               >> lit(')'))
-         [push_back(_val,construct<mapnik::filter::agg_stack_blur>(_a,_b))])
-        |
         lit("invert")[push_back(_val,construct<mapnik::filter::invert>())]
+        |
+        agg_blur_filter(_val)
+        |
+        hsla_filter(_val)
         ;
+
+    agg_blur_filter = (lit("agg-stack-blur")[_a = 1, _b = 1]
+        >> -( lit('(') >> radius_[_a = _1]
+              >> lit(',')
+              >> radius_[_b = _1]
+              >> lit(')')))
+        [push_back(_r1,construct<mapnik::filter::agg_stack_blur>(_a,_b))]
+        ;
+
+    hsla_filter = (lit("hsla") >> lit('(') >> string_arg[_a = _1] >> lit(')'))
+        [push_back(_r1,construct<mapnik::filter::hsla>(_a))]
+        ;
+
+    string_arg = +~char_(')');
 }
 
 template struct mapnik::image_filter_grammar<std::string::const_iterator,std::vector<mapnik::filter::filter_type> >;