gistfile1.js

var imageAutoresizeConfig = {
  types: '**/*.{jpg,jpeg,png}',
  versions : [
    {
      width: 640,
      suffix: '_mobile'
    }, {
      width: 800,
      suffix: '_medium'
    }
  ]
};

 // TODO: implement imagemin etc., autoresizing etc.
gulp.task('images', [], function(done) {

  var stream = gulp.src(paths.images, {
    base: paths.app
  })
    .pipe(g.if(isProduction, g.imagemin()))
    .pipe(gulp.dest(paths.dist));

  // autoresizing if configured

  var versions = imageAutoresizeConfig.versions || [];
  if (imageAutoresizeConfig && imageAutoresizeConfig.types) {

    stream = stream.pipe(g.filter(imageAutoresizeConfig.types));

    versions.forEach(function(version) {

      stream = stream.pipe(parallel(
        g.imageResize({ width: version.width }),
        os.cpus().length
      ))
      .pipe(g.rename(function(path) {
        if (path.extname !== '') {
          path.basename += version.suffix;
        }
      }))
      .pipe(gulp.dest(paths.dist));
    });
  }

  return stream;

});