anchor.diff:  
   stdenv.mkDerivation rec {
     name = "libpng-${version}";
  -  version = "1.6.21";
  +  version = "1.6.22";
   
     src = fetchurl {
       url = "mirror://sourceforge/libpng/libpng-${version}.tar.xz";
  -    sha256 = "10r0xqasm8fi0dx95bpca63ab4myb8g600ypyndj2r4jxd4ii3vc";
  +    allowHashOutput = false;
  +    multihash = "QmU3V85XU2KWpwXQzwSUbekrcgvXJFsKHttBQwwrrpAcaX";
  +    sha256 = "6b5a6ad5c5801ec4d24aacc87a0ed7b666cd586478174f69368a1d7747715226";
     };
   
     buildInputs = [
  
positive.code:   patches = [
      (fetchurl {
        url = "mirror://sourceforge/libpng-apng/libpng-${version}-apng.patch.gz";
        sha256 = "0wwcc52yzjaxvpfkicz20j7yzpy02hpnsm4jjlvw74gy4qjhx9vd";
      })
    ];
  
    meta = with stdenv.lib; {
      description = "The official reference implementation for the PNG file format with animation patch";
  
negative.code:       wkennington
      ];
      platforms = with platforms;
        x86_64-linux;
    };
  }
  