title: gulp-imagemin: Couldn't load default plugin xxx
body: <p>the env:</p>
  
  <ul>
  <li>windows 7</li>
  <li>node 6.9.5</li>
  </ul>
  
  <p>I use the plugin like <a href="https://www.npmjs.com/package/gulp-imagemin" rel="nofollow noreferrer">this npm</a>. but I get an error. from some video, It's correct. It's relative to imagemin's version?</p>
  
  <pre><code>// gulpfile.js
  
  var gulp = require('gulp');
  var imagemin = require('gulp-imagemin');
  
  var app = {
    srcPath: 'src/',
    devPath: 'build/',
    prdPath: 'dist/', //生产部署
  }
  gulp.task('image', function() {
    gulp.src(app.srcPath + 'image/**/*')
    .pipe(gulp.dest(app.devPath + 'image'))
    .pipe(imagemin())
    .pipe(gulp.dest(app.prdPath + 'image'))
  })
  </code></pre>
  
  <p>when I "gulp image", got an error:</p>
  
  <pre><code>[13:05:56] Using gulpfile ~\Desktop\study\angularapp\gulpfile.js
  [13:05:56] Starting 'image'...
  [13:05:56] Finished 'image' after 6.96 ms
  [13:05:56] gulp-imagemin: Couldn't load default plugin "gifsicle"
  [13:05:56] gulp-imagemin: Couldn't load default plugin "jpegtran"
  [13:05:56] gulp-imagemin: Couldn't load default plugin "optipng"
  [13:05:56] gulp-imagemin: Minified 1 image (saved 0 B - 0%)
  </code></pre>
  
  <p>I use <code>npm install imagemin-optipng</code>, But it still doesn't work.
  dependencies like this:</p>
  
  <pre><code>"devDependencies": {
  "clean-css": "^4.0.5",
  "gulp": "^3.9.1",
  "gulp-clean": "^0.3.2",
  "gulp-concat": "^2.6.1",
  "gulp-connect": "^5.0.0",
  "gulp-cssmin": "^0.1.7",
  "gulp-imagemin": "^3.1.1",
  "gulp-less": "^3.3.0",
  "gulp-load-plugins": "^1.5.0",
  "gulp-uglify": "^2.0.1",
  "lodash": "^4.17.4",
  "open": "^0.0.5"
  </code></pre>
  
  <p>}</p>
  
  <p>what happend to it?</p>