improve EPS aliasing
diff --git a/coders/json.c b/coders/json.c
index 13a2928..1645912 100644
--- a/coders/json.c
+++ b/coders/json.c
@@ -321,7 +321,7 @@
       register ssize_t
         i;
 
-      if (GetPixelReadMask(image,p) == 0)
+      if (GetPixelReadMask(image,p) <= (QuantumRange/2))
         {
           p+=GetPixelChannels(image);
           continue;