Gulp: Adv. Gulp workflow http://ahmadawais.com/my-advanced-gulp-workflow-for-wordpress-themes/

gulpfile.js

/**
 *
 * Gulpfile setup
 *
 * @since 1.0.0
 * @authors Ahmad Awais, @digisavvy, @desaiuditd, @jb510, @dmassiani and @Maxlopez
 * @package neat
 * @forks _s & some-like-it-neat
 */


// Project configuration
var project 		= 'neat', // Project name, used for build zip.
	url 			= 'neat.dev', // Local Development URL for BrowserSync. Change as-needed.
	bower 			= './assets/bower_components/'; // Not truly using this yet, more or less playing right now. TO-DO Place in Dev branch
	build 			= './buildtheme/', // Files that you want to package into a zip go here
	buildInclude 	= [
						// include common file types
						'**/*.php',
						'**/*.html',
						'**/*.css',
						'**/*.js',
						'**/*.svg',
						'**/*.ttf',
						'**/*.otf',
						'**/*.eot',
						'**/*.woff',
						'**/*.woff2',

						// include specific files and folders
						'screenshot.png',

						// exclude files and folders
						'!node_modules/**/*',
						'!assets/bower_components/**/*',
						'!style.css.map',
						'!assets/js/custom/*',
						'!assets/css/patrials/*'

					];

// Load plugins
	var gulp     = require('gulp'),
		browserSync  = require('browser-sync'), // Asynchronous browser loading on .scss file changes
		reload       = browserSync.reload,
		autoprefixer = require('gulp-autoprefixer'), // Autoprefixing magic
		minifycss    = require('gulp-uglifycss'),
		filter       = require('gulp-filter'),
		uglify       = require('gulp-uglify'),
		imagemin     = require('gulp-imagemin'),
		newer        = require('gulp-newer'),
		rename       = require('gulp-rename'),
		concat       = require('gulp-concat'),
		notify       = require('gulp-notify'),
		cmq          = require('gulp-combine-media-queries'),
		runSequence  = require('gulp-run-sequence'),
		sass         = require('gulp-sass'),
		plugins      = require('gulp-load-plugins')({ camelize: true }),
		ignore       = require('gulp-ignore'), // Helps with ignoring files and directories in our run tasks
		rimraf       = require('gulp-rimraf'), // Helps with removing files and directories in our run tasks
		zip          = require('gulp-zip'), // Using to zip up our packaged theme into a tasty zip file that can be installed in WordPress!
		plumber      = require('gulp-plumber'), // Helps prevent stream crashing on errors
		cache        = require('gulp-cache'),
		sourcemaps   = require('gulp-sourcemaps');


/**
 * Browser Sync
 *
 * Asynchronous browser syncing of assets across multiple devices!! Watches for changes to js, image and php files
 * Although, I think this is redundant, since we have a watch task that does this already.
*/
gulp.task('browser-sync', function() {
	var files = [
					'**/*.php',
					'**/*.{png,jpg,gif}'
				];
	browserSync.init(files, {

		// Read here http://www.browsersync.io/docs/options/
		proxy: url,

		// port: 8080,

		// Tunnel the Browsersync server through a random Public URL
		// tunnel: true,

		// Attempt to use the URL "http://my-private-site.localtunnel.me"
		// tunnel: "ppress",

		// Inject CSS changes
		injectChanges: true

	});
});



/**
 * Styles
 *
 * Looking at src/sass and compiling the files into Expanded format, Autoprefixing and sending the files to the build folder
 *
 * Sass output styles: https://web-design-weekly.com/2014/06/15/different-sass-output-styles/
*/
gulp.task('styles', function () {
 	gulp.src('./assets/css/*.scss')
		.pipe(plumber())
		.pipe(sourcemaps.init())
		.pipe(sass({
			errLogToConsole: true,
	
			//outputStyle: 'compressed',
			outputStyle: 'compact',
			// outputStyle: 'nested',
			// outputStyle: 'expanded',
			precision: 10
		}))
		.pipe(sourcemaps.write({includeContent: false}))
		.pipe(sourcemaps.init({loadMaps: true}))
		.pipe(autoprefixer('last 2 version', '> 1%', 'safari 5', 'ie 8', 'ie 9', 'opera 12.1', 'ios 6', 'android 4'))
		.pipe(sourcemaps.write('.'))
		.pipe(plumber.stop())
		.pipe(gulp.dest('./'))
		.pipe(filter('**/*.css')) // Filtering stream to only css files
		.pipe(cmq()) // Combines Media Queries
		.pipe(reload({stream:true})) // Inject Styles when style file is created
		.pipe(rename({ suffix: '.min' }))
		.pipe(minifycss({
			maxLineLen: 80
		}))
		.pipe(gulp.dest('./'))
		.pipe(reload({stream:true})) // Inject Styles when min style file is created
		.pipe(notify({ message: 'Styles task complete', onLast: true }))
});


/**
 * Scripts: Vendors
 *
 * Look at src/js and concatenate those files, send them to assets/js where we then minimize the concatenated file.
*/
gulp.task('vendorsJs', function() {
	return 	gulp.src(['./assets/js/vendor/*.js', bower+'**/*.js'])
				.pipe(concat('vendors.js'))
				.pipe(gulp.dest('./assets/js'))
				.pipe(rename( {
					basename: "vendors",
					suffix: '.min'
				}))
				.pipe(uglify())
				.pipe(gulp.dest('./assets/js/'))
				.pipe(notify({ message: 'Vendor scripts task complete', onLast: true }));
});


/**
 * Scripts: Custom
 *
 * Look at src/js and concatenate those files, send them to assets/js where we then minimize the concatenated file.
*/

gulp.task('scriptsJs', function() {
	return 	gulp.src('./assets/js/custom/*.js')
				.pipe(concat('custom.js'))
				.pipe(gulp.dest('./assets/js'))
				.pipe(rename( {
					basename: "custom",
					suffix: '.min'
				}))
				.pipe(uglify())
				.pipe(gulp.dest('./assets/js/'))
				.pipe(notify({ message: 'Custom scripts task complete', onLast: true }));
});


/**
 * Images
 *
 * Look at src/images, optimize the images and send them to the appropriate place
*/
gulp.task('images', function() {

// Add the newer pipe to pass through newer images only
	return 	gulp.src(['./assets/img/raw/**/*.{png,jpg,gif}'])
				.pipe(newer('./assets/img/'))
				.pipe(rimraf({ force: true }))
				.pipe(imagemin({ optimizationLevel: 7, progressive: true, interlaced: true }))
				.pipe(gulp.dest('./assets/img/'))
				.pipe( notify( { message: 'Images task complete', onLast: true } ) );
});


/**
 * Clean gulp cache
 */
 gulp.task('clear', function () {
   cache.clearAll();
 });


 /**
  * Clean tasks for zip
  *
  * Being a little overzealous, but we're cleaning out the build folder, codekit-cache directory and annoying DS_Store files and Also
  * clearing out unoptimized image files in zip as those will have been moved and optimized
 */

 gulp.task('cleanup', function() {
 	return 	gulp.src(['./assets/bower_components', '**/.sass-cache','**/.DS_Store'], { read: false }) // much faster
		 		.pipe(ignore('node_modules/**')) //Example of a directory to ignore
		 		.pipe(rimraf({ force: true }))
		 		// .pipe(notify({ message: 'Clean task complete', onLast: true }));
 });
 gulp.task('cleanupFinal', function() {
 	return 	gulp.src(['./assets/bower_components','**/.sass-cache','**/.DS_Store'], { read: false }) // much faster
		 		.pipe(ignore('node_modules/**')) //Example of a directory to ignore
		 		.pipe(rimraf({ force: true }))
		 		// .pipe(notify({ message: 'Clean task complete', onLast: true }));
 });

 /**
  * Build task that moves essential theme files for production-ready sites
  *
  * buildFiles copies all the files in buildInclude to build folder - check variable values at the top
  * buildImages copies all the images from img folder in assets while ignoring images inside raw folder if any
  */

  gulp.task('buildFiles', function() {
  	return 	gulp.src(buildInclude)
 		 		.pipe(gulp.dest(build))
 		 		.pipe(notify({ message: 'Copy from buildFiles complete', onLast: true }));
  });


/**
* Images
*
* Look at src/images, optimize the images and send them to the appropriate place
*/
gulp.task('buildImages', function() {
	return 	gulp.src(['assets/img/**/*', '!assets/images/raw/**'])
		 		.pipe(gulp.dest(build+'assets/img/'))
		 		.pipe(plugins.notify({ message: 'Images copied to buildTheme folder', onLast: true }));
});

 /**
  * Zipping build directory for distribution
  *
  * Taking the build folder, which has been cleaned, containing optimized files and zipping it up to send out as an installable theme
 */
 gulp.task('buildZip', function () {
 	// return 	gulp.src([build+'/**/', './.jshintrc','./.bowerrc','./.gitignore' ])
 	return 	gulp.src(build+'/**/')
		 		.pipe(zip(project+'.zip'))
		 		.pipe(gulp.dest('./'))
		 		.pipe(notify({ message: 'Zip task complete', onLast: true }));
 });


 // ==== TASKS ==== //
 /**
  * Gulp Default Task
  *
  * Compiles styles, fires-up browser sync, watches js and php files. Note browser sync task watches php files
  *
 */

 // Package Distributable Theme
 gulp.task('build', function(cb) {
 	runSequence('styles', 'cleanup', 'vendorsJs', 'scriptsJs',  'buildFiles', 'buildImages', 'buildZip','cleanupFinal', cb);
 });


 // Watch Task
 gulp.task('default', ['styles', 'vendorsJs', 'scriptsJs', 'images', 'browser-sync'], function () {
 	gulp.watch('./assets/img/raw/**/*', ['images']); 
 	gulp.watch('./assets/css/**/*.scss', ['styles']);
 	gulp.watch('./assets/js/**/*.js', ['scriptsJs', browserSync.reload]);

 });

Hi @ahmadawais!
Do u have any idea how to optimize all images wp-content/uploads directory?