anchor.diff:    NIX_CFLAGS_COMPILE = lib.optional enableEXR "-I${ilmbase.dev}/include/OpenEXR";
   
     cmakeFlags = [
  -    "-DBUILD_PROTOBUF=OFF"
  -    "-DPROTOBUF_UPDATE_FILES=ON"
       "-DWITH_OPENMP=ON"
       (opencvFlag "IPP" enableIpp)
       (opencvFlag "TIFF" enableTIFF)
  
positive.code: }:
  
  let
    version = "3.3.0";
  
    src = fetchFromGitHub {
      owner  = "opencv";
      repo   = "opencv";
      rev    = version;
      sha256 = "0266kg337wij9rz602z5088jn2fq56aqpxxflf0fbh28kygchvk4";
    };
  
    contribSrc = fetchFromGitHub {
      owner  = "opencv";
      repo   = "opencv_contrib";
      rev    = version;
      sha256 = "0qxdvzdszzlpsya1pn4d2r9z4j98isxrgk15a2wwa3dqjmgv880d";
    };
  
    # Contrib must be built in order to enable Tesseract support:
  
negative.code:     '');
  
    buildInputs =
         [ zlib pcre hdf5 ]
      ++ lib.optional enablePython pythonPackages.python
      ++ lib.optional enableGtk2 gtk2
      ++ lib.optional enableGtk3 gtk3
  