Gruntfile.js

module.exports = function(grunt) {

  grunt.initConfig({
    responsive_images: {
      dev: {
        options: {
          //engine: 'gm',
          sizes: [{
            name: '480',
            width: 480,
            //suffix: '-480',
            quality: 20
          },{
            name: '800',
            width: 800,
						//suffix: '-800',
						rename: false,
            quality: 40
          }]
        },
        files: [{
          expand: true,
          src: ['*.{gif,jpg,png}'],
          cwd: 'src/img_src/',
          dest: 'src/img/'
        }]
      }
		},
		
		/* Clear out the images directory if it exists */
    clean: {
      dev: {
        src: ['img'],
      },
		},
		
		/* Generate the images directory if it is missing */
    mkdir: {
      dev: {
        options: {
          create: ['img']
        },
      },
		},
		
		/* Copy the "fixed" images that don't go through processing into the images/directory */
    copy: {
      dev: {
        files: [{
          expand: true,
          src: ['src/img_src/fixed/*.{gif,jpg,png}'],
          dest: 'src/img/',
          flatten: true,
        }]
      },
    },
  });

	grunt.loadNpmTasks('grunt-responsive-images');
	grunt.loadNpmTasks('grunt-contrib-clean');
	grunt.loadNpmTasks('grunt-contrib-copy');
  grunt.loadNpmTasks('grunt-mkdir');
  grunt.registerTask('default', ['clean', 'mkdir', 'copy', 'responsive_images']);

};