How to resize image size in nodejs using multer

Question

Multer have already limit size property. This property only restrict the image. Not resize the image. My question is suppose image is greater than "limit size", how to resize that image ?

var storageOptions = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, 'useravatars/')
  },
  filename: function (req, file, cb) {
    cb(null, file.fieldname + '-' + Date.now())
  }
});

var avatarUpload = multer({
    storage: storageOptions,
    limits: {
        fileSize: 1000000
    }
}).single("avatar");

Answer 1

It depends on whether you want to store the resized image as well.

In any case, you'll use a library to handle the resize operation. sharp is a very good option.

Resize in a route handler(after file is stored to disk):

sharp(req.file).resize(200, 200).toBuffer(function(err, buf) {
  if (err) return next(err)

  // Do whatever you want with `buf`
})

Other option would be creating your own storage engine, in this case you'll receive the file data, resize, then store to disk (copied from https://github.com/expressjs/multer/blob/master/StorageEngine.md):

var fs = require('fs')

function getDestination(req, file, cb) {
  cb(null, '/dev/null')
}

function MyCustomStorage(opts) {
  this.getDestination = (opts.destination || getDestination)
}

MyCustomStorage.prototype._handleFile = function _handleFile(req, file, cb) {
  this.getDestination(req, file, function(err, path) {
    if (err) return cb(err)

    var outStream = fs.createWriteStream(path)
    var resizer = sharp().resize(200, 200).png()

    file.stream.pipe(resizer).pipe(outStream)
    outStream.on('error', cb)
    outStream.on('finish', function() {
      cb(null, {
        path: path,
        size: outStream.bytesWritten
      })
    })
  })
}

MyCustomStorage.prototype._removeFile = function _removeFile(req, file, cb) {
  fs.unlink(file.path, cb)
}

module.exports = function(opts) {
  return new MyCustomStorage(opts)
}

Answer 2

const path = require("path");
const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, path.join(__dirname, "/uploads"));
  },
  filename: function (req, file, cb) {
    cb(null, uuid.v4() + `${path.extname(file.originalname)}`);
  }
});

const limits = {
  fields: 10,
  fileSize: 500 * 1024,
  files: 1,
};

const upload = multer({ storage, limits });
const baseUrl = "http://localhost:3000/files/";
router.post("/upload", upload.single("file"), async (ctx, next) => {
  ctx.body = {
    code: 1,
    data: baseUrl + ctx.file.filename,
  };
});