Imagemin plugin for Webpack

This is a simple plugin that uses Imagemin to compress all images in your project.

Install

npm install imagemin-webpack-plugin

Requires node >=4.0.0

Example Usage

var ImageminPlugin = require('imagemin-webpack-plugin').default
// Or if using ES2015:
// import ImageminPlugin from 'imagemin-webpack-plugin'

module.exports = {
  plugins: [
    // Make sure that the plugin is after any plugins that add images
    new ImageminPlugin({
      disable: process.env.NODE_ENV !== 'production', // Disable during development
      pngquant: {
        quality: '95-100'
      }
    })
  ]
}

Working with copy-webpack-plugin:

module.exports = {
  plugins: [
    // Copy the images folder and optimize all the images
    new CopyWebpackPlugin([{
      from: 'images/'
    }]),
    new ImageminPlugin({ test: /\.(jpe?g|png|gif|svg)$/i })
  ]
}

Note the order of the plugins matters. ImageminWebpackPlugin must be placed after CopyWebpackPlugin (or any other plugins that deal with images) in plugins array.

API

new ImageminPlugin(options)

options.disable

type: Boolean default: false

When set to true it will disable the plugin entirely. This is useful for disabling the plugin during development, and only enabling it during production

options.test

type: RegExp or String or Array default: /.*/

This plugin will only run on files that match this test. This is similar to the webpack loader test option (but is not using the same implementation, so there might be major differences!). This can either be a RegExp object, a minimatch glob, a function which gets the filename and returns true if the file should be minified, or an array of any of them.

This can allow you to only run the plugin on specific files, or even include the plugin multiple times for different sets of images and apply different imagemin settings to each.

This will overwrite everything, including the externalImages option!

Example:

import ImageminPlugin from 'imagemin-webpack-plugin'

module.exports = {
  plugins: [
    // Use the default settings for everything in /images/*
    new ImageminPlugin({ test: 'images/**' }),
    // bump up the optimization level for all the files in my `bigpngs` directory
    new ImageminPlugin({
      test: 'bigpngs/**',
      optipng: {
        optimizationLevel: 9
      }
    })
  ]
}

options.maxConcurrency

type: Number default: the number of logical CPUS on the system

Sets the maximum number of instances of Imagemin that can run at once. Set to Infinity to run a seperate process per image all at the same time.

options.optipng

type: Object or null default: { optimizationLevel: 3 }

Passes the given object to imagemin-optipng. Set to null to disable optipng.

options.gifsicle

type: Object or null default: { optimizationLevel: 1 }

Passes the given object to imagemin-gifsicle. Set to null to disable gifsicle.

options.jpegtran

type: Object or null default: { progressive: false }

Passes the given object to imagemin-jpegtran. Set to null to disable jpegtran.

options.svgo

type: Object or null default: {}

Passes the given object to imagemin-svgo. Set to null to disable svgo.

options.pngquant

type: Object or null default: null

Passes the given object to imagemin-pngquant. Disabled by default.

options.plugins

type: Array default: []

Include any additional plugins that you want to work with imagemin here. By default the above are included, but if you want (or need to) you can disable them (by setting them to null) and include them yourself here.

A list of possible imagemin plugins can be found here.

Example:

import ImageminPlugin from 'imagemin-webpack-plugin'
import imageminMozjpeg from 'imagemin-mozjpeg'

module.exports = {
  plugins: [
    new ImageminPlugin({
      plugins: [
        imageminMozjpeg({
          quality: 100,
          progressive: true
        })
      ]
    })
  ]
}

options.externalImages

type: Object default: { context: '.', sources: [], destination: null, fileName: null }

Include any external images (those not included in webpack's compilation assets) that you want to be parsed by imagemin. If a destination value is not supplied the files are optimized in place. You can optionally set either of these to a function which will be invoked at the last possible second before optimization to grab files that might not exist at the time of writing the config (see #37 for more info).

The paths will work based on the webpack's (and this plugin's) context option, so in the following example, the files will be read from ./src/images/**/*.png and will be written to .src/public/images/**/*.png Context only applies to the sources array.

Example:

import ImageminPlugin from 'imagemin-webpack-plugin'
import glob from 'glob'

module.exports = {
  plugins: [
    new ImageminPlugin({
      externalImages: {
        context: 'src', // Important! This tells the plugin where to "base" the paths at
        sources: glob.sync('src/images/**/*.png'),
        destination: 'src/public/images',
        fileName: '[path][name].[ext]' // (filePath) => filePath.replace('jpg', 'webp') is also possible
      }
    })
  ]
}

options.minFileSize

type: Integer default: 0

Only apply to images that are larger than this value in bytes.

options.maxFileSize

type: Integer default: Infinity

Only apply to images that are smaller than or equal-to this value in bytes.

This and minFileSize together can be used to include WebpackImageminPlugin multiple times with multiple configs on different file sizes.

Example:

import ImageminPlugin from 'imagemin-webpack-plugin'
import glob from 'glob'

module.exports = {
  plugins: [
    new ImageminPlugin({
      maxFileSize: 10000, // Only apply this one to files equal to or under 10kb
      jpegtran: { progressive: false }
    }),
    new ImageminPlugin({
      minFileSize: 10000, // Only apply this one to files over 10kb
      jpegtran: { progressive: true }
    })
  ]
}

options.cacheFolder

type: String default: ''

Cache already minified images into a cacheFolder. On next run plugin will check for the cached images first. If cached image exists it will simply use that one. Otherwise image will be optimised and written to the cacheFolder for later builds.

Note: This is a very simple cache implementation, it WILL NOT intelligently clear the cache if you update the options in this plugin. There also might be significantly more files in the cache than you have images, this is normal, and a side-effect of how I'm deferring to imagemin to determine if a file is an image or not. It can be prevented by setting a good test regex.

Example:

import resolve from 'path'
import ImageminPlugin from 'imagemin-webpack-plugin'

module.exports = {
  plugins: [
    new ImageminPlugin({
      cacheFolder: resolve('./cache'), // use existing folder called cache in the current dir
    })
  ]
}

options.onlyUseIfSmaller

type: Boolean default: false

If set to true, this plugin will use the original image if the optimization process makes it larger.

true used to be the default behavior in version 2 of this plugin!

Troubleshooting

If you get an error similar to Error in parsing SVG: Unquoted attribute value while using SVGO, you most likely have un-quoted attributes in the SVG image. A workaround can be found here from @vzaidman. They also made an issue upstream which should fix it at the source here.

FAQ

Why? I was suprised that there weren't any Imagemin plugins for webpack, so I made one!

Why not use image-webpack-loader? Because I had other things like the favicons-webpack-plugin and responsive-loader that were generating images that I couldn't have image-webpack-loader optimize. This plugin will optimize ANY images regardless of how they were added to webpack. Plus image-webpack-loader is currently using an older version of imagemin.

Can you add this new feature? Maybe... I'm trying to keep this a small single-purpose plugin, but if you want a feature feel free to open an issue and I'll take a look.

Inspiration

• Big thanks to image-webpack-loader for the idea.
• Used compression-webpack-plugin to learn how to write the plugin. It's source code is a better tutorial on how to write plugins than the webpack documentation is...

Contributing

See the CONTRIBUTING file here

License

MIT Copyright (c) Gregory Benner