enhance scale-hsla validation - refs #1954

include/mapnik/image_filter_types.hpp

@@ -71,10 +71,14 @@ struct scale_hsla
       l1(_l1),
       a0(_a0),
       a1(_a1) {
-          if (h0 < 0 || h1 > 1 ||
+          if (h0 < 0 || h0 > 1 ||
-              s0 < 0 || s1 > 1 ||
+              h1 < 0 || h1 > 1 ||
-              l0 < 0 || l1 > 1 ||
+              s0 < 0 || s0 > 1 ||
-              a0 < 0 || a1 > 1)
+              s1 < 0 || s1 > 1 ||
+              l0 < 0 || l0 > 1 ||
+              l1 < 0 || l1 > 1 ||
+              a0 < 0 || a0 > 1 ||
+              a1 < 0 || a1 > 1)
           {
               throw config_error("scale-hsla values must be between 0 and 1");
           }