code: function readPNG(file) {
      const deferred = Q.defer();
      const onerror = deferred.reject.bind(deferred);
      const stream = fs.createReadStream(file);
      stream.on("error", onerror);
      pngparse.parseStream(stream, function(err, image) {
          if (err) {
              console.log("Failed to load " + file);
              onerror(err);
              return;
          }
          deferred.resolve(image);
      });
      return deferred.promise;
  }
docs: Read given file and parse it as a PNG file.