imgproxy is a fast and secure standalone server for resizing and converting remote images. The main principles of imgproxy are simplicity, speed, and security.
imgproxy can be used to provide a fast and secure way to replace all the image resizing code of your web application (like calling ImageMagick or GraphicsMagick, or using libraries), while also being able to resize everything on the fly, fast and easy. imgproxy is also indispensable when handling lots of image resizing, especially when images come from a remote source.
imgproxy does one thing — resizing remote images — and does it well. It works great when you need to resize multiple images on the fly to make them match your application design without preparing a ton of cached resized images or re-doing it every time the design changes.
imgproxy is a Go application, ready to be installed and used in any Unix environment — also ready to be containerized using Docker.
* It would be great to be able to rotate, flip and apply masks to images, but in most of the cases, it is possible — and is much easier — to do that using CSS3.
* It may be great to have built-in HTTP caching of some kind, but it is way better to use a Content-Delivery Network or a caching proxy server for this, as you will have to do this sooner or later in the production environment.
* It might be useful to have everything built in — such as HTTPS support — but an easy way to solve that would be just to use a proxying HTTP server such as nginx.
imgproxy uses probably the most efficient image processing library there is, called `libvips`. It is screaming fast and has a very low memory footprint; with it, we can handle the processing for a massive amount of images on the fly.
Massive processing of remote images is a potentially dangerous thing, security-wise. There are many attack vectors, so it is a good idea to consider attack prevention measures first. Here is how imgproxy can help:
* imgproxy checks image type _and_ "real" dimensions when downloading, so the image will not be fully downloaded if it has an unknown format or the dimensions are too big (there is a setting for that). That is how imgproxy protects you from so called "image bombs" like those described at https://www.bamsoftware.com/hacks/deflate.html.
* imgproxy supports authorization by an HTTP header. That prevents using imgproxy directly by an attacker but allows to use it through a CDN or a caching server — just by adding a header to a proxy or CDN config.
Great bunch of kudos goes to [John Cupitt](https://github.com/jcupitt) who develops [libvips](https://github.com/libvips/libvips) and helps me to optimize its usage under the hood of imgproxy.
