anchor.diff:    ade = rec {
       src = fetchurl {
         url = "https://github.com/opencv/ade/archive/${name}";
  -      sha256 = "1r85vdkvcka7bcxk69pd0ai4hld4iakpj4xl0xbinx3p9pv5a4l8";
  -    };
  -    name = "v0.1.1d.zip";
  -    md5 = "37479d90e3a5d47f132f512b22cbe206";
  +      sha256 = "04n9na2bph706bdxnnqfcbga4cyj8kd9s9ni7qyvnpj5v98jwvlm";
  +    };
  +    name = "v0.1.1f.zip";
  +    md5 = "b624b995ec9c439cbc2e9e6ee940d3a2";
       dst = ".cache/ade";
     };
   
  
positive.code: }:
  
  let
    version = "4.1.0";
  
    src = fetchFromGitHub {
      owner  = "opencv";
      repo   = "opencv";
      rev    = version;
      sha256 = "0m1f51m11iz4vxfrmnhawksd669ld247rlfdq5fhkvfk3r7aidw6";
    };
  
    contribSrc = fetchFromGitHub {
      owner  = "opencv";
      repo   = "opencv_contrib";
      rev    = version;
      sha256 = "1phmmba96m5znjf3wxwhxavgzgp3bs5qqsjk9ay1i63rdacz4vlf";
    };
  
    # Contrib must be built in order to enable Tesseract support:
  
negative.code:   postUnpack = lib.optionalString buildContrib ''
      cp --no-preserve=mode -r "${contribSrc}/modules" "$NIX_BUILD_TOP/source/opencv_contrib"
    '';
  
    # This prevents cmake from using libraries in impure paths (which
    # causes build failure on non NixOS)
  