anchor.diff:  
     enableParallelBuilding = true;
   
  -  # Workaround for: https://github.com/opencv/opencv/issues/10474
  -  preBuild = ''
  -    make opencv_dnn
  -  '';
  -
     postBuild = lib.optionalString enableDocs ''
       make doxygen
     '';
  
positive.code: { lib, stdenv
  , fetchurl, fetchFromGitHub
  , cmake, pkgconfig, unzip, zlib, pcre, hdf5
  , caffe, glog, boost, google-gflags, protobuf
  , config
  
negative.code: stdenv.mkDerivation rec {
    name = "opencv-${version}";
    inherit version src;
  
    patches = [
      # Fix for: https://github.com/opencv/opencv/issues/10474
      (fetchpatch {
        url = "https://github.com/opencv/opencv/commit/ea5a3e557f93844fdb5e54e3e8acfc5f61c6fd9f.patch";
        sha256 = "1w7jmqlrx73ydh9jjsnnic5xz8r04kxbjpzkcfyb91v3az9132r1";
      })
    ];
  
    postUnpack = lib.optionalString buildContrib ''
      cp --no-preserve=mode -r "${contribSrc}/modules" "$NIX_BUILD_TOP/opencv_contrib"
  