gulpfile.js

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

gulp.task("default", function() {

  var normal = gulp.src( destination + '*.png' );
  var retina = normal.pipe(clone());

  normal.pipe(makeSprites())
    .pipe(gulp.dest( imagesBase + '1x/' ));

  retina.pipe(makeSprites('retina'))
    .pipe(gulp.dest( imagesBase + '2x/' )); 

});

function makeSprites(nameExtension) {
  var name = 'sprite';
  if( typeof( nameExtension ) !== 'undefined' ) { 
    name += '-' + nameExtension;
  }
  
  return sprite({
      name: name,
      style: '_' + name + '.scss',
      cssPath: imagesBase,
      processor: 'scss'
  })
  .pipe(imagemin({
    optimizationLevel: 5,
    progressive: true,
    interlaced: true
  }));
}