picfit

picfit is a reusable Go server to manipulate (resize, thumbnail, etc.) images built on top of negroni and gorilla mux.

It will act as a proxy of your storage engine and will be served ideally behind an http cache system like varnish.

It supports multiple storages backends and multiple key/value stores.

Installation

Build it

1. Make sure you have a Go language compiler >= 1.3 (required) and git installed.
2. Make sure you have the following go system dependencies in your $PATH: bzr, svn, hg, git
3. Ensure your GOPATH is properly set.
4. Download it:

git clone https://github.com/thoas/picfit.git

4. Run make build

You have now a binary version of picfit in the bin directory which fits perfectly with your architecture.

Debian and Ubuntu

We will provide Debian package when we will be completely stable ;)

Configuration

Configuration should be stored in a readable file and in JSON format.

config.json

{
  "kvstore": {
    "type": "[KVSTORE]"
  },
  "storage": {
    "src": {
      "type": "[STORAGE]"
    }
  }
}

[KVSTORE] can be:

• redis - Store generated keys in Redis, see below how you can customize connection parameters
• cache - Store generated keys in an in-memory cache

[STORAGE] can be:

• fs - Store generated images in your File system
• http+fs - Store generated images in your File system and loaded using HTTP protocol
• s3 - Store generated images in Amazon S3
• http+s3 - Store generated images in Amazon S3 and loaded using HTTP protocol

Basic

• no key/value store
• no image storage
• images are given in absolute url

config.json

{
  "port": 3001,
}

Images are generated on the fly at each request

Store images on file system and keys in an in-memory cache

• key/value in-memory store
• file system storage

An image is generated from your source storage (src) and uploaded asynchronously to this storage.

A unique key is generated and stored in a in-memory key/value store to process a dedicated request only once.

config.json

{
  "port": 3001,
  "storage": {
    "src": {
      "type": "fs",
      "location": "/path/to/directory/"
    }
  },
  "kvstore": {
    "type": "cache"
  },
}

Store images on Amazon S3, keys in Redis and shard filename

• key/value store provided by Redis
• Amazon S3 storage
• shard filename

config.json

{
  "kvstore": {
    "type": "redis",
    "host": "127.0.0.1",
    "port": "6379",
    "password": "",
    "db": 0
  },
  "port": 3001,
  "storage": {
    "src": {
      "type": "s3",
      "access_key_id": "[ACCESS_KEY_ID]",
      "secret_access_key": "[SECRET_ACCESS_KEY]",
      "bucket_name": "[BUCKET_NAME]",
      "acl": "[ACL]",
      "region": "[REGION_NAME]",
      "location": "path/to/directory"
    }
  },
  "shard": {
    "width": 1,
    "depth": 2
  }
}

Keys will be stored on Redis, (you better setup persistence).

Image files will be loaded and stored on Amazon S3 at the location path/to/directory in the bucket [BUCKET_NAME].

[ACL] can be:

• private
• public-read
• public-read-write
• authenticated-read
• bucket-owner-read
• bucket-owner-full-control

[REGION_NAME] can be:

• us-gov-west-1
• us-east-1
• us-west-1
• us-west-2
• eu-west-1
• eu-central-1
• ap-southeast-1
• ap-southeast-2
• ap-northeast-1
• sa-east-1
• cn-north-1

Filename will be sharded:

• depth - 2 directories
• width - 1 letter for each directory

Example:

06102586671300cd02ae90f1faa16897.png will become 0/6/102586671300cd02ae90f1faa16897.jpg

It would be useful if you are using the file system storage backend.

Load images from file system and store them in Amazon S3, keys on Redis

• key/value store provided by Redis
• File system to load images
• Amazon S3 storage to process images

config.json

{
  "kvstore": {
    "type": "redis",
    "host": "127.0.0.1",
    "port": "6379",
    "password": "",
    "db": 0
  },
  "port": 3001,
  "storage": {
    "src": {
      "type": "fs",
      "location": "path/to/directory"
    },
    "dst": {
      "type": "s3",
      "access_key_id": "[ACCESS_KEY_ID]",
      "secret_access_key": "[SECRET_ACCESS_KEY]",
      "bucket_name": "[BUCKET_NAME]",
      "acl": "[ACL]",
      "region": "[REGION_NAME]",
      "location": "path/to/directory"
    }
  }
}

You will be able to load and store your images from different storages backend.

In this example, images will be loaded from the file system storage and generated to the Amazon S3 storage.

Load images from storage backend base url, store them in Amazon S3, keys prefixed on Redis

• key/value store provided by Redis
• File system to load images using HTTP method
• Amazon S3 storage to process images

config.json

{
  "kvstore": {
    "type": "redis",
    "host": "127.0.0.1",
    "port": "6379",
    "password": "",
    "prefix": "dummy:",
    "db": 0
  },
  "port": 3001,
  "storage": {
    "src": {
      "type": "http+fs",
      "base_url": "http://media.example.com",
      "location": "path/to/directory"
    },
    "dst": {
      "type": "s3",
      "access_key_id": "[ACCESS_KEY_ID]",
      "secret_access_key": "[SECRET_ACCESS_KEY]",
      "bucket_name": "[BUCKET_NAME]",
      "acl": "[ACL]",
      "region": "[REGION_NAME]",
      "location": "path/to/directory"
    }
  }
}

In this example, images will be loaded from the file system storage using HTTP with base_url option and generated to the Amazon S3 storage.

Keys will be stored on Redis using the prefix dummy:.

Running

To run the application, issue the following command:

$ picfit -c config.json

By default, this will run the application on port 3001 and can be accessed by visiting:

http://localhost:3001

The port number can be configured with port option in your config file.

To see a list of all available options, run:

$ picfit --help

Usage

General parameters

Parameters to call the picfit service are:

<img src="http://localhost:3001/{method}?url={url}&path={path}&w={width}&h={height}&upscale={upscale}&sig={sig}&op={operation}&fmt={format}&q={quality}&deg={degree}&pos={position}"

• path - The filepath to load the image using your source storage
• operation - The operation to perform, see Operations
• sig - The signature key which is the representation of your query string and your secret key, see Security
• method - The method to perform, see Methods
• url - The url of the image to generate (not required if path provided)
• width - The desired width of the image, if 0 is provided the service will calculate the ratio with height
• height - The desired height of the image, if 0 is provided the service will calculate the ratio with width
• upscale - If your image is smaller than your desired dimensions, the service will upscale it by default to fit your dimensions, you can disable this behavior by providing 0
• format - The output format to save the image, by default the format will be the source format (a GIF image source will be saved as GIF), see Formats
• quality - The quality to save the image, by default the quality will be the highest possible, it will be only applied on JPEG format
• degree - The degree (90, 180, 270) to rotate the image
• position - The position to flip the image

To use this service, include the service url as replacement for your images, for example:

<img src="https://www.google.fr/images/srpr/logo11w.png" />

will become:

<img src="http://localhost:3001/display?url=https%3A%2F%2Fwww.google.fr%2Fimages%2Fsrpr%2Flogo11w.png&w=100&h=100&op=resize&upscale=0"

This will retrieve the image used in the url parameter and resize it to 100x100.

Using source storage

If an image is stored in your source storage at the location path/to/file.png, then you can call the service to load this file:

<img src="http://localhost:3001/display?w=100&h=100&path=path/to/file.png&op=resize"

or

<img src="http://localhost:3001/display/resize/100x100/path/to/file.png"

Formats

picfit currently supports the following formats:

• image/jpeg with the keyword jpg or jpeg
• image/png with the keyword png
• image/gif with the keyword gif
• image/bmp with the keyword bmp

Operations

Resize

This operation will able you to resize the image to the specified width and height.

If width or height value is 0, the image aspect ratio is preserved.

• w - The desired image's width
• h - The desired image's height

You have to pass the resize value to the op parameter to use this operation.

Thumbnail

Thumbnail scales the image up or down using the specified resample filter, crops it to the specified width and height and returns the transformed image.

• w - The desired width of the image
• h - The desired height of the image

You have to pass the thumbnail value to the op parameter to use this operation.

Flip

Flip flips the image vertically (from top to bottom) or horizontally (from left to right) and returns the transformed image.

• pos - The desired position to flip the image, h will flip the image horizontally, v will flip the image vertically

You have to pass the flip value to the op parameter to use this operation.

Rotate

Rotate rotates the image to the desired degree and returns the transformed image.

• deg - The desired degree to rotate the image

You have to pass the rotate value to the op parameter to use this operation.

Methods

Display

Display the image, useful when you are using an img tag.

The generated image will be stored asynchronously on your destination storage backend.

A couple of headers (Content-Type, If-Modified-Since) will be set to allow you to use an http cache system.

Redirect

Redirect to an image.

Your file will be generated synchronously then the redirection will be performed.

The first query will be slower but next ones will be faster because the name of the generated file will be stored in your key/value store.

Get

Retrieve information about an image.

Your file will be generated synchronously then you will get the following information:

• filename - Filename of your generated file
• path - Path of your generated file
• url - Absolute url of your generated file (only if base_url is available on your destination storage)

The first query will be slower but next ones will be faster because the name of the generated file will be stored in your key/value store.

Expect the following result:

{
    "filename":"a661f8d197a42d21d0190d33e629e4.png",
    "path":"cache/6/7/a661f8d197a42d21d0190d33e629e4.png",
    "url":"https://ds9xhxfkunhky.cloudfront.net/cache/6/7/a661f8d197a42d21d0190d33e629e4.png"
}

Upload

Upload is disabled by default for security reason. Before enabling it, you must understand you have to secure yourself this endpoint like only allowing the /upload route in your nginx or apache webserver for the local network.

Exposing the /upload endpoint without a security mechanism is not SAFE.

You can enable it by adding the option and a source storage to your configuration file.

config.json

{
  "storage": {
    "src": {
      "type": "[STORAGE]"
    }
  },
  "options": {
    "enable_upload": true
  }
}

Test it with the excellent httpie:

http -f POST localhost:3000/upload data@myupload

You will retrieve the uploaded image information in JSON format.

Security

In order to secure requests and avoid unknown third parties to use the service, the application can require a request to provide a signature. To enable this feature, set the secret_key option in your config file.

The signature is an hexadecimal digest generated from the client key and the query string using the HMAC-SHA1 message authentication code (MAC) algorithm.

The below python code provides an implementation example:

import hashlib
import hmac
import six
import urllib

def sign(key, *args, **kwargs):
    m = hmac.new(key, None, hashlib.sha1)

    for arg in args:
        if isinstance(arg, dict):
            m.update(urllib.urlencode(arg))
        elif isinstance(arg, six.string_types):
            m.update(arg)

    return m.hexdigest()

The signature is passed to the application by appending the sig parameter to the query string; e.g. w=100&h=100&sig=c9516346abf62876b6345817dba2f9a0c797ef26.

Note, the application does not include the leading question mark when verifying the supplied signature. To verify your signature implementation, see the signature command described in the Tools section.

Tools

To verify that your client application is generating correct signatures, use the command:

$ picfit signature --key=abcdef "w=100&h=100&op=resize"
Query String: w=100&h=100&op=resize
Signature: 6f7a667559990dee9c30fb459b88c23776fad25e
Signed Query String: w=100&h=100&op=resize&sig=6f7a667559990dee9c30fb459b88c23776fad2

Error reporting

picfit logs events by default in stderr and stdout. You can implement sentry to log errors using raven.

To enable this feature, set sentry option in your config file.

config.json

{
  "sentry": {
    "dsn": "[YOUR_SENTRY_DSN]",
    "tags": {
      "foo": "bar"
    }
  }
}

Debug

Debug is disabled by default.

To enable this feature set debug option to true in your config file:

config.json

{
  "debug": true
}

CORS

picfit supports CORS headers customization in your config file.

To enable this feature, set allowed_origins and allowed_methods, for example:

config.json

{
  "allowed_origins": ["*.ulule.com"],
  "allowed_methods": ["GET", "HEAD"]
}

Options

Quality

The quality rendering of the image engine can be controlled globally without adding it at each request:

config.json

{
  "options": {
    "quality": 70
  }
}

With this option, each image will be saved in 70 quality.

By default the quality is the highest possible: 95

Format

The format can be forced globally without adding it at each request:

config.json

{
  "options": {
    "format": "png"
  }
}

With this option, each image will be forced to be saved in .png.

By default the format will be chosen in this order:

• The fmt parameter if exists in query string
• The original image format
• The default format provided in the application

Upload

The upload handler is disabled by default for security reason, you can enable it in your config:

config.json

{
  "options": {
    "enable_upload": true
  }
}

Deployment

It's recommended that the application run behind a CDN for larger applications or behind varnish for smaller ones.

Provisioning is handled by Ansible, you will find files in the repository.

You must have Ansible installed on your laptop, basically if you have python already installed you can do

$ pip install ansible

If you want to run the installed version from vagrant

$ vagrant up

Then connect to vagrant

$ vagrant ssh

The config is located to /etc/picfit/config.json on the vagrant box.

Roadmap

see issues

Don't hesitate to send patch or improvements.

Clients

Client libraries will help you generate picfit urls with your secret key.

• picfit-go: a Go client library

In production

• Ulule: an european crowdfunding platform

Inspirations

• pilbox
• thumbor
• trousseau

Thanks to these beautiful projects.