gulp-scale-images

Gulp plugin to make each image smaller. Combined with flat-map, you can create multiple variantes per image, which is useful for responsive images.

Installing

npm install gulp-scale-images --save-dev

Usage

gulp-scale-images expects the instructions for each file to be in file.scale. They may look like this:

{
	maxWidth: 300, // optional maximum width
	maxHeight: 400, // optional maximum height
	format: 'jpeg', // optional, one of ('jpeg', 'png', 'webp')
	withoutEnlargement: false, // optional, default is true
	fit: 'inside', // optional, default is 'cover', one of ('cover', 'contain', 'fill', 'inside', 'outside')
	rotate: true, // optional
	metadata: false, // copy metadata over?
	formatOptions: {} // optional, additional format options for sharp engine
}

Note: You must specify at least one of maxWidth and maxHeight.

You can pass additional format options to Sharp engine using formatOptions parameter. Docs can be found at Sharp API.

An example, we're going to generate two smaller variants for each input file. We're going to use flat-map for this:

const gulp = require('gulp')
const flatMap = require('flat-map').default
const scaleImages = require('gulp-scale-images')

const twoVariantsPerFile = (file, cb) => {
	const pngFile = file.clone()
	pngFile.scale = {maxWidth: 500, maxHeight: 500, format: 'png'}
	const jpegFile = file.clone()
	jpegFile.scale = {maxWidth: 700, format: 'jpeg'}
	cb(null, [pngFile, jpegFile])
}

gulp.src('src/*.{jpeg,jpg,png,gif}')
.pipe(flatMap(twoVariantsPerFile))
.pipe(scaleImages())
.pipe(gulp.dest(…))

Note: Unlike sharp, gulp-scale-image is not designed to process untrusted user input. For example, it turns off sharp's input pixel limit altogether.

Definining scale instructions based on metadata

You can let gulp-scale-images read the image metadata first, to device what to do with the file:

const readMetadata = require('gulp-scale-images/read-metadata')
const through = require('through2')
const scaleImages = require('gulp-scale-images')

const computeScaleInstructions = (file, _, cb) => {
	readMetadata(file, (err, meta) => {
		if (err) return cb(err)
		file = file.clone()
		file.scale = {
			maxWidth: Math.floor(meta.width / 2),
			maxHeight: Math.floor(meta.height / 2)
		}
		cb(null, file)
	})
}

gulp.src(…)
.pipe(through.obj(computeScaleInstructions))
.pipe(scaleImages())
.pipe(gulp.dest(…))

Custom output file names

By default, gulp-scale-images will use {basename}.{maxWidth}w-{maxHeight}h.{format} (e.g. foo.500w-300h.jpeg). You can define a custom logic though:

const path = require('path')
const scaleImages = require('gulp-scale-images')

const computeFileName = (output, scale, cb) => {
	const fileName = [
		path.basename(output.path, output.extname), // strip extension
		scale.maxWidth + 'w',
		scale.format || output.extname
	].join('.')
	cb(null, fileName)
}

gulp.src(…)
.pipe(through.obj(computeScaleInstructions))
.pipe(scaleImages(computeFileName)) // not that we pass computeFileName here
.pipe(gulp.dest(…))

gulp-scale-images works well with

• flat-map – A flat map implementation for node streams. (One chunk in, n chunks out.)
• replace-ext – Replaces a file extension with another one.

Similar libraries

Some similar libraries and why I think this one is better.

• gulp-image-resize
  • uses gm instead of sharp, requires gm to be installed
  • supports only one scale instruction
• gulp-sharp
  • is not being maintained
  • has no tests
  • supports only one scale instruction
• gulp-retinize
  • doesn't seem to be maintained
  • uses gm instead of sharp, requires gm to be installed
  • only works for files on disk
  • supports only one scale instruction
• gulp-imgconv
  • has no tests
  • supports only one scale instruction
• gulp-inline-resize
  • doesn't do one thing
  • uses gm instead of sharp, requires gm to be installed
• gulp-unretina
  • less flexible
  • uses gm instead of sharp, requires gm to be installed
• gulp-gm-limit
  • doesn't seem to be maintained
  • supports only one scale instruction
• gulp-imgresize
  • no documentation
  • is not being maintained
  • has no tests

Contributing

If you have a question or have difficulties using gulp-scale-images, please double-check your code and setup first. If you think you have found a bug or want to propose a feature, refer to the issues page.