[libpng16] Added missing parentheses to a macro definition
(Contributed by github.com/irwir)
diff --git a/pngwrite.c b/pngwrite.c
index e526cba..b91d04d 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1636,7 +1636,7 @@
* calculation can be done to 15 bits of accuracy; however, the output needs to
* be scaled in the range 0..255*65535, so include that scaling here.
*/
-# define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)
+# define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+((alpha)>>1))/(alpha))
static png_byte
png_unpremultiply(png_uint_32 component, png_uint_32 alpha,
