diff -ruN enblend.orig/Makefile enblend/Makefile
--- enblend.orig/Makefile	2017-05-26 14:38:20.772640000 +0200
+++ enblend/Makefile	2017-05-26 14:38:37.844744000 +0200
@@ -17,6 +17,7 @@
 BUILD_DEPENDS=	help2man:misc/help2man \
 		OpenEXR>=1.0:graphics/OpenEXR
 LIB_DEPENDS=	liblcms2.so:graphics/lcms2 \
+		libpng.so:graphics/png \
 		libtiff.so:graphics/tiff \
 		libboost_filesystem.so:devel/boost-libs \
 		libvigraimpex.so:graphics/vigra \