Gruntfile.js

'use strict';

const imageminJpegRecompress = require('imagemin-jpeg-recompress');

module.exports = function (grunt) {
  grunt.initConfig({
    pkg: grunt.file.readJSON('package.json'),
    imagemin: {
      imgs: {
        options: {
          use: [
            imageminJpegRecompress({
              method: 'ms-ssim',
              quality: 'veryhigh'
            })
          ]
        },
        files: [{
          // Set to true to enable the following options…
          expand: true,
          cwd: '_site/',
          src: ['**/*.{jpg,png,gif,svg}'],
          dest: '_site/'
        }]
      },
    },
    banner: '/*!\n' +
    ' * <%= pkg.title %> v<%= pkg.version %> (<%= pkg.homepage %>)\n' +
    ' * Copyright <%= grunt.template.today("yyyy") %> <%= pkg.author %>\n' +
    ' * Licensed under <%= pkg.license %> (https://spdx.org/licenses/<%= pkg.license %>)\n' +
    ' */\n',
    usebanner: {
      dist: {
        options: {
          position: 'top',
          banner: '<%= banner %>'
        },
        files: {
          src: [
            '_site/assets/**.css',
            '_site/assets/**.js'
          ]
        }
      }
    },
    watch: {
      scripts: {
        files: ['_site/img/**.jpg'],
        tasks: ['default'],
        options: {
          spawn: false,
        },
      },
    },
  });

  grunt.loadNpmTasks('grunt-contrib-imagemin');
  grunt.loadNpmTasks('grunt-banner');
  grunt.loadNpmTasks('grunt-contrib-watch');

  grunt.registerTask('default', ['imagemin', 'usebanner']);
};