diff --git a/src/graphics.cpp b/src/graphics.cpp
index 71a19b068..c7e320c50 100644
--- a/src/graphics.cpp
+++ b/src/graphics.cpp
@@ -93,7 +93,22 @@ image_32::~image_32() {}
 
 void image_32::set_grayscale_to_alpha()
 {
+    for (int y = 0; y < height_; ++y)
+    {
+        unsigned int* row_from = data_.getRow(y);
+        for (int x = 0; x < width_; ++x)
+        {
+            unsigned rgba = row_from[x];
+            unsigned r = rgba & 0xff;
+            unsigned g = (rgba >> 8 ) & 0xff;
+            unsigned b = (rgba >> 16) & 0xff;
+            
+            // magic numbers for grayscale
+            unsigned a = (int)((r * .3) + (g * .59) + (b * .11));
 
+            row_from[x] = (a << 24)| (255 << 16) |  (255 << 8) | (255) ;
+        }
+    }
 }
 
 void image_32::set_color_to_alpha(const color& c)
@@ -113,8 +128,7 @@ void image_32::set_alpha(float opacity)
 
 #ifdef MAPNIK_BIG_ENDIAN
             unsigned a0 = (rgba & 0xff);
-            //unsigned a1 = int( (rgba & 0xff) * opacity );
-            unsigned a1 = opacity;
+            unsigned a1 = int( (rgba & 0xff) * opacity );
 
             if (a0 == a1) continue;
 
@@ -126,8 +140,8 @@ void image_32::set_alpha(float opacity)
 
 #else
             unsigned a0 = (rgba >> 24) & 0xff;
-            //unsigned a1 = int( ((rgba >> 24) & 0xff) * opacity );
-            unsigned a1 = opacity;
+            unsigned a1 = int( ((rgba >> 24) & 0xff) * opacity );
+            //unsigned a1 = opacity;
             if (a0 == a1) continue;
 
             unsigned r = rgba & 0xff;