anchor.diff:      ++ lib.optional enableFfmpeg ffmpeg
       ++ lib.optionals enableGStreamer (with gst_all; [ gstreamer gst-plugins-base ])
       ++ lib.optional enableEigen eigen
  +    ++ lib.optionals stdenv.isDarwin (with darwin.apple_sdk.frameworks; [ Cocoa QTKit ])
       ;
   
     propagatedBuildInputs = lib.optional enablePython pythonPackages.numpy;
  
positive.code: 
    passthru = lib.optionalAttrs enablePython { pythonPath = []; };
  
    meta = {
      description = "Open Computer Vision Library with more than 500 algorithms";
      homepage = http://opencv.org/;
      license = stdenv.lib.licenses.bsd3;
      maintainers = with stdenv.lib.maintainers; [viric flosse];
      platforms = with stdenv.lib.platforms; linux;
    };
  }
  
negative.code: , enableJPEG ? true, libjpeg
  , enablePNG ? true, libpng
  , enableTIFF ? true, libtiff
  , enableEXR ? (!stdenv.isDarwin), openexr, ilmbase
  , enableJPEG2K ? true, jasper
  , enableFfmpeg ? false, ffmpeg
  , enableGStreamer ? false, gst_all
  , enableEigen ? false, eigen
  , darwin
  }:
  
  let
  