anchor.diff:    patches = [
       (fetchurl {
         url = "mirror://sourceforge/libpng-apng/libpng16/${version}/${name}-apng.patch.gz";
  -      sha256 = "e661944e54574a3f26927ac9eb7e2788f3a2675545a19735b83fbb9adcb544c1";
  +      sha256 = "18ceb239857bbd32ca706cdad29f1a5dcfb87a5c54258db3bb077cff78c12e04";
       })
     ];
   
  
positive.code: }:
  
  let
    version = "1.6.34";
  in
  stdenv.mkDerivation rec {
    name = "libpng-${version}";
  
negative.code:   src = fetchurl {
      url = "mirror://sourceforge/libpng/libpng16/${version}/${name}.tar.xz";
      hashOutput = false;
      sha256 = "23912ec8c9584917ed9b09c5023465d71709dce089be503c7867fec68a93bcd7";
    };
  
    buildInputs = [
  