Gulp

var gulp = require('gulp');
var imageResize = require('gulp-image-resize');

var paths = {
  images: "source/images/**/*"
}

gulp.task('images', function() {

    gulp.src(['source/images/**/*.png', 'source/images/**/*.jpg'])
        .pipe(imageResize({
            width: 538,
            height: 538
        }))
        .pipe(gulp.dest('tmp/dist/assets/images/538x538'));

    gulp.src(['source/images/**/*.png', 'source/images/**/*.jpg'])
        .pipe(imageResize({
            width: 1076,
            height: 1076
        }))
        .pipe(gulp.dest('tmp/dist/assets/images/1076x1076'));

});

gulp.task('watch', function() {
  gulp.watch(paths.images, ['images']);
});

gulp.task('default', ['watch', 'images']);
gulp.task('build', ['images']);