Imager

Image processing proxy server written in Elixir.

Why?

We needed to generate thumbnails for various files in one of our client's product. We have tried to use SNS channel to produce them for new images only however this approach has few disadvantages:

• you need to specify all needed image sizes upfront, so any change in needed sizes requires redeployment of UI and image processing service
• configuration of given application is quite complicated as it requires several manual steps; this is especially troublesome in our situation as our application need simple way to deploy by unskilled sysop on-premise

With given requirements we could use one of existing on-demand image processing services like:

• Thumbor, quite popular service written in Python which uses OpenCV bindings to process images
• Imaginary, written in Go wrapper over libvips library
• Imageflow, written in Rust, AGPL reimplementation of ImageResizer

However we also needed support for PDFs and DICOM images which is available only in Imaginary. However the API of the Imaginary do not provide enough flexibility, Imageflow/ImageResizer-like API is much easier to integrate with UI. Imageflow would be a perfect solution (even despite AGPL license), however lack of PDF and DICOM support made it completely infeasible in our situation.

Production ready?

No. We use it in our production release, but it is still prone to rapid changes in the API. Current API is direct mapping to ImageMagick options, however in future releases we probably provide higher level API more similar to Imageflow which would allow us to provide support for different processing libraries, not only ImageMagick.

Installation

Docker

Currently the only officially supported installation way is via official Docker image that can be found on Docker Hub.

1. First we need to generate configuration file for Imager

$ docker run --rm appunite/imager:latest config > config.toml

1. Edit config.toml. Documentation is available within the file itself.
2. Run container providing configuration.

$ docker run --rm -v './config.toml:/etc/imager/config.toml:ro' -p 8080:80 appunite/imager:latest

Usage

Assuming that you have store named local and there is file named lenna.png you can access this file directly via on http://localhost:8080/local/lenna.png, to generate thumbnail of size 50x50 pixels you can then use http://localhost:8080/local/lenna.png?thumbnail=50x50.

Currently available options are:

• thumbnail=<size>
• strip
• gravity=<gravity>
• extent=<size>
• flatten
• background=<colour>
• format=<format>

Which maps 1:1 to their respective ImageMagick flags.

License

See LICENSE file.