multer and gm - upload and save multiple images with varios resolutions (nodejs, express)

.js

import multer from 'multer'
import passportManager from '../../config/passport'
import fs from 'fs'
import gm from 'gm'
import mime from 'mime'
import 'array-foreach-async'

const storage = multer.diskStorage({
    destination: function (req, file, cb) {
        const { params: { folder, subfolder } } = req

        if (!fs.existsSync(`${__dirname}/../../public/images/${folder}`)) {
            fs.mkdirSync(`${__dirname}/../../public/images/${folder}`);
        }

        if (!fs.existsSync(`${__dirname}/../../public/images/${folder}/${subfolder}`)) {
            fs.mkdirSync(`${__dirname}/../../public/images/${folder}/${subfolder}`);
        }

        cb(null, `${__dirname}/../../public/images/${folder}/${subfolder}`)
    },
    filename: function (req, file, cb) {
        const { params: { filename } } = req
        cb(null, filename)
    }
})

const upload = multer({ storage: storage })
const resizeImage = (width, height, path, outPath) => new Promise((resolve, reject) => {
    gm(path)
        .resize(width, height, '^')
        .gravity('Center')
        .extent(width, height)
        .noProfile()
        .write(outPath, function (err) {
            if (err) {
                reject(err)
            }

            resolve({
                result: true
            })
        })
})

export default app => { // app is express
    app.route('/upload/single/:folder/:subfolder/:filename')
        .post(upload.single('image'), function (req, res) {
            const { params: { filename }, file } = req
            const ext = mime.getExtension(file.mimetype)
            const save = file.destination
            let savedImgs = []
            const sizes = [
                {
                    width: 300,
                    height: 250,
                    prefix: `-300-250px`
                },
                {
                    width: 336,
                    height: 280,
                    prefix: `-336-280px`
                },
                {
                    width: 800,
                    height: 600,
                    prefix: `-800-600px`
                },
            ]

            if (!fs.existsSync(save)) {
                fs.mkdirSync(save);
            }

            sizes.forEachAsync(async ({ width, height, prefix }, i) => {

                await resizeImage(width, height, file.path, `${save}/${filename}${prefix}.${ext}`)
                const relPath = `${save}/${filename}${prefix}.${ext}`.split('/images/').pop()

                savedImgs.push({
                    src: relPath,
                    width,
                    height
                })

                if (i === (sizes.length - 1)) {
                    fs.unlink(file.path, function (err) {
                        if (err)
                            throw err

                        return res.status(200).send({ result: true, savedImgs })
                    })
                }
            })
        })

}

First you must install gm on your OS, for example in ubuntu

sudo add-apt-repository ppa:dhor/myway
sudo apt-get update
sudo apt-get install graphicsmagick