Fix for negative radius.
diff --git a/MagickCore/accelerate.c b/MagickCore/accelerate.c
index b3ba492..239618d 100644
--- a/MagickCore/accelerate.c
+++ b/MagickCore/accelerate.c
@@ -1801,7 +1801,7 @@
     {
       imageColumns = (unsigned int) image->columns;
       imageRows = (unsigned int) image->rows;
-      iRadius = (cl_int) radius;
+      iRadius = (cl_int) fabs(radius);
 
       passes = ((1.0f * imageColumns) * imageColumns * iRadius) / 4000000000.0f;
       passes = (passes < 1) ? 1: passes;