mongoose-crate-gm

A mongoose-crate FileProcessor that applies image transformations with GraphicsMagick via the gm module.

Prequisites

A modern version of GraphicsMagic installed and available on the path.

Usage

You can pass images through one or more filters:

const mongoose = require('mongoose')
const crate = require('mongoose-crate')
const LocalFS = require('mongoose-crate-localfs')
const GraphicsMagic = require('mongoose-crate-gm')

const PostSchema = new mongoose.Schema({
  title: String,
  description: String
})

PostSchema.plugin(crate, {
  storage: new LocalFS({
    directory: '/path/to/storage/directory'
  }),
  fields: {
    image: {
      processor: new GraphicsMagic({
        tmpDir: '/tmp', // Where transformed files are placed before storage, defaults to os.tmpdir()
        formats: ['JPEG', 'GIF', 'PNG'], // Supported formats, defaults to ['JPEG', 'GIF', 'PNG', 'TIFF']
        transforms: {
          original: {
            // keep the original file
          },
          small: {
            resize: '150x150',
            format: '.jpg'
          },
          medium: {
            resize: '250x250',
            format: '.jpg'
          }
        }
      })
    }
  }
})

const Post = mongoose.model('Post', PostSchema)

.. then later:

const post = new Post()
post.attach('image', {path: '/path/to/image'}, (error) => {
  // image is now attached and post.image is populated e.g.:
  // post.image.small.url
  // post.image.medium.url
})

Meta data

mongoose-crate-gm extends the basic meta data added by mongoose-crate to add some image specific fields. It provides the following for each transformation:

{
  width: 120,
  height: 103,
  depth: 8,
  format: 'PNG',
  name: 'dragon.png',
  size: 26887,
  url: 'http://my_bucket.s3.amazonaws.com/folder/4fbaaa31db8cec0923000019-medium.png'
}

Transformations

Transformations are achieved by invoking the convert command and passing all the properties of the transform as arguments.

Example in convert command:

gm convert source.png -crop 120x120 -blur 5x10 output.png

Example in plugin options:

PostSchema.plugin(crate, {
  ...
  fields: {
    image: {
      processor: new GraphicsMagic({
        transforms: {
          small: {
            crop: '120x120',
            blur: '5x10'

For more information on available transforms, see the GraphicsMagick website.

Changing the destination format

You can change the destination format by using the special transform property format with a known file extension like png, jpg, gif, etc:

PostSchema.plugin(crate, {
  ...
  fields: {
    image: {
      processor: new GraphicsMagic({
        transforms: {
          as_jpeg: {
            format: 'jpg'

Supported formats

By default we'll only try to process a few common image types. The supported list defaults to jpgs, pngs, gifs and tiffs.

This list can be overridden by specifying the formats argument:

PostSchema.plugin(crate, {
  ...
  fields: {
    image: {
      processor: new GraphicsMagic({
        formats: ['JPEG', 'GIF', 'PNG']

The values should match up with convert's supported formats. To see a list of all formats supported by your install, run:

gm convert -list format

Using ImageMagick instead of GraphicsMagic

By default the gm module uses the GraphicsMagic binary. If you wish to use ImageMagick instead, first install a recent version of ImageMagick on your system and add it to your path, then pass true for the imageMagick option:

PostSchema.plugin(crate, {
  ...
  fields: {
    image: {
      processor: new GraphicsMagic({
        imageMagick: true