--- src/plugins/imagemagick.cpp	2013-03-18 14:21:49.848848166 +0900
+++ src/plugins/imagemagick.cpp.new	2013-03-18 15:37:57.502107423 +0900
@@ -124,10 +124,10 @@
 
       for(int x = 0; x < width; ++x)
       {
-        dst_pixels[4*x + 0] = static_cast<uint8_t>(src_pixels[x].red   >> shift);
-        dst_pixels[4*x + 1] = static_cast<uint8_t>(src_pixels[x].green >> shift);
-        dst_pixels[4*x + 2] = static_cast<uint8_t>(src_pixels[x].blue  >> shift);
-        dst_pixels[4*x + 3] = static_cast<uint8_t>(255 - (src_pixels[x].opacity >> shift));
+        dst_pixels[4*x + 0] = static_cast<uint8_t>(src_pixels[x].red / QuantumRange * QuantumRange);
+        dst_pixels[4*x + 1] = static_cast<uint8_t>(src_pixels[x].green / QuantumRange * QuantumRange);
+        dst_pixels[4*x + 2] = static_cast<uint8_t>(src_pixels[x].blue  / QuantumRange * QuantumRange);
+        dst_pixels[4*x + 3] = static_cast<uint8_t>(255 - (src_pixels[x].opacity / QuantumRange * QuantumRange));
       }
     }
   }
@@ -142,9 +142,9 @@
 
       for(int x = 0; x < width; ++x)
       {
-        dst_pixels[3*x + 0] = static_cast<uint8_t>(src_pixels[x].red   >> shift);
-        dst_pixels[3*x + 1] = static_cast<uint8_t>(src_pixels[x].green >> shift);
-        dst_pixels[3*x + 2] = static_cast<uint8_t>(src_pixels[x].blue  >> shift);
+        dst_pixels[3*x + 0] = static_cast<uint8_t>(src_pixels[x].red / QuantumRange * QuantumRange);
+        dst_pixels[3*x + 1] = static_cast<uint8_t>(src_pixels[x].green / QuantumRange * QuantumRange);
+        dst_pixels[3*x + 2] = static_cast<uint8_t>(src_pixels[x].blue / QuantumRange * QuantumRange);
       }
     }
   }