shrink.js

#!/usr/bin/env node

const fs = require('fs');
const path = require('path');

function error(message) {
  console.error(message);
  process.exit();

}

if (process.argv.length != 4) {
  error("Use: shrink FROM_PATH TO_PATH");
}

var from = path.resolve(process.argv[2]);
var to = path.resolve(process.argv[3]);

if(!fs.existsSync(from) || !fs.lstatSync(from).isDirectory()) {
  error(process.argv[2] + " is not a valid directory");
}

if(!fs.existsSync(to) || !fs.lstatSync(to).isDirectory()) {
  error(process.argv[3] + " is not a valid directory");
}

const gulp = require('gulp');
const imagemin = require('gulp-imagemin');
const pngquant = require('imagemin-pngquant'); // $ npm i -D imagemin-pngquant

gulp.task('default', function(){
    return gulp.src([from + '/**/*.png',from + '/**/*.jpg',from + '/**/*.jpeg',from + '/**/*.gif'])
        .pipe(imagemin({
            progressive: true,
            svgoPlugins: [
                {removeViewBox: false},
                {cleanupIDs: false}
            ],
            use: [pngquant()]
        }))
        .pipe(gulp.dest(to));
});

gulp.start('default');
console.log('Starting to minify png and jpg from ' + from);

#Install dependencies

npm install gulp
npm install gulp-imagemin
npm install imagemin-pngquant

#give it execute permission
chmod +x ./shrink

#run
./shrink IMAGES_DIR OUTPUT_DIR