anchor.diff:  }:
   
   let
  -  version = "1.6.36";
  +  version = "1.6.37";
   in
   stdenv.mkDerivation rec {
     name = "libpng-${version}";
  
positive.code:   patches = [
      (fetchurl {
        url = "mirror://sourceforge/libpng-apng/libpng16/${version}/${name}-apng.patch.gz";
        sha256 = "8c1f33da739b29a77e35e5a1ebcdffaab63bfe184be8b5a97677cc80156fdc0f";
      })
    ];
  
  
negative.code:   src = fetchurl {
      url = "mirror://sourceforge/libpng/libpng16/${version}/${name}.tar.xz";
      hashOutput = false;
      sha256 = "505e70834d35383537b6491e7ae8641f1a4bed1876dbfe361201fc80868d88ca";
    };
  
    buildInputs = [
  