var retinize = require('gulp-retinize');

gulp.task('retiniizing', function(file) {
  /* NOTE: Retinize accepts @4x and @2x resolutions, outputting to @4x, @2x, and @1x.
  Overrides may be implemented by manually creating lower resolution copies in the source directory. */
  const retinizeOpts = {
      // Your options here.
  };

  console.log('Retinizing images...');

  return gulp.src(file && file.path || './path/to/your/sprites/*.{png,jpg,jpeg}')
    .pipe(retinize(retinizeOpts))
    .on('error', function(e) {
      console.log(e.message);
    })
    .pipe(gulp.dest('./path/to/your/sprites/'));
});