# imageproxy [![Build Status](https://travis-ci.org/willnorris/imageproxy.svg?branch=master)](https://travis-ci.org/willnorris/imageproxy) [![GoDoc](https://godoc.org/willnorris.com/go/imageproxy?status.svg)](https://godoc.org/willnorris.com/go/imageproxy) [![Apache 2.0 License](https://img.shields.io/badge/license-Apache%202.0-blue.svg?style=flat)](LICENSE) imageproxy is a caching image proxy server written in go. It features: - basic image adjustments like resizing, cropping, and rotation - access control using host whitelists or request signing (HMAC-SHA256) - support for jpeg, png, webp (decode only), and gif image formats (including animated gifs) - on-disk caching, respecting the cache headers of the original images - easy deployment, since it's pure go Personally, I use it primarily to dynamically resize images hosted on my own site (read more in [this post][]). But you can also enable request signing and use it as an SSL proxy for remote images, similar to [atmos/camo][] but with additional image adjustment options. [this post]: https://willnorris.com/2014/01/a-self-hosted-alternative-to-jetpacks-photon-service [atmos/camo]: https://github.com/atmos/camo ## URL Structure ## imageproxy URLs are of the form `http://localhost/{options}/{remote_url}`. ### Options ### Options are available for resizing, rotation, flipping, and digital signatures among a few others. Options for are specified as a comma delimited list of parameters, which can be supplied in any order. Duplicate parameters overwrite previous values. See the full list of available options at . ### Remote URL ### The URL of the original image to load is specified as the remainder of the path, without any encoding. For example, `http://localhost/200/https://willnorris.com/logo.jpg`. In order to [optimize caching][], it is recommended that URLs not contain query strings. [optimize caching]: http://www.stevesouders.com/blog/2008/08/23/revving-filenames-dont-use-querystring/ ### Examples ### The following live examples demonstrate setting different options on [this source image][small-things], which measures 1024 by 678 pixels. [small-things]: https://willnorris.com/2013/12/small-things.jpg Options | Meaning | Image --------|------------------------------------------|------ 200x | 200px wide, proportional height |

x0.15 | 15% original height, proportional width |

100x150 | 100 by 150 pixels, cropping as needed |

100 | 100px square, cropping as needed |

150,fit | scale to fit 150px square, no cropping |

100,r90 | 100px square, rotated 90 degrees |

100,fv,fh | 100px square, flipped horizontal and vertical |

200x,q60 | 200px wide, proportional height, 60% quality |

200x,png | 200px wide, converted to PNG format |

Transformation also works on animated gifs. Here is [this source image][material-animation] resized to 200px square and rotated 270 degrees: [material-animation]: https://willnorris.com/2015/05/material-animations.gif

## Getting Started ## Install the package using: go get willnorris.com/go/imageproxy/cmd/imageproxy (Note that go1.2 and earlier may have trouble fetching the package with `go get`). Once installed, ensure `$GOPATH/bin` is in your `$PATH`, then run the proxy using: imageproxy This will start the proxy on port 8080, without any caching and with no host whitelist (meaning any remote URL can be proxied). Test this by navigating to and you should see a 500px square coder octocat. ### Cache ### By default, the imageproxy command does not cache responses, but caching can be enabled using the `-cache` flag. It supports the following values: - `memory` - uses an in-memory cache. (This can exhaust your system's available memory and is not recommended for production systems) - directory on local disk (e.g. `/tmp/imageproxy`) - will cache images on disk - s3 URL (e.g. `s3://s3-us-west-2.amazonaws.com/my-bucket`) - will cache images on Amazon S3. This requires either an IAM role and instance profile with access to your your bucket or `AWS_ACCESS_KEY_ID` and `AWS_SECRET_KEY` environmental parameters set. For example, to cache files on disk in the `/tmp/imageproxy` directory: imageproxy -cache /tmp/imageproxy Reload the [codercat URL][], and then inspect the contents of `/tmp/imageproxy`. Within the subdirectories, there should be two files, one for the original full-size codercat image, and one for the resized 500px version. [codercat URL]: http://localhost:8080/500/https://octodex.github.com/images/codercat.jpg ### Referrer Whitelist ### You can limit images to only be accessible for certain hosts in the HTTP referrer header, which can help prevent others from hotlinking to images. It can be enabled by running: imageproxy -referrers example.com Reload the [codercat URL][], and you should now get an error message. You can specify multiple hosts as a comma separated list, or prefix a host value with `*.` to allow all sub-domains as well. ### Host whitelist ### You can limit the remote hosts that the proxy will fetch images from using the `whitelist` flag. This is useful, for example, for locking the proxy down to your own hosts to prevent others from abusing it. Of course if you want to support fetching from any host, leave off the whitelist flag. Try it out by running: imageproxy -whitelist example.com Reload the [codercat URL][], and you should now get an error message. You can specify multiple hosts as a comma separated list, or prefix a host value with `*.` to allow all sub-domains as well. ### Signed Requests ### Instead of a host whitelist, you can require that requests be signed. This is useful in preventing abuse when you don't have just a static list of hosts you want to allow. Signatures are generated using HMAC-SHA256 against the remote URL, and url-safe base64 encoding the result: base64urlencode(hmac.New(sha256, ).digest()) The HMAC key is specified using the `signatureKey` flag. If this flag begins with an "@", the remainder of the value is interpreted as a file on disk which contains the HMAC key. Try it out by running: imageproxy -signatureKey "secret key" Reload the [codercat URL][], and you should see an error message. Now load a [signed codercat URL][] and verify that it loads properly. [signed codercat URL]: http://localhost:8080/500,sXyMwWKIC5JPCtlYOQ2f4yMBTqpjtUsfI67Sp7huXIYY=/https://octodex.github.com/images/codercat.jpg Some simple code samples for generating signatures in various languages can be found in [URL Signing](https://github.com/willnorris/imageproxy/wiki/URL-signing). If both a whiltelist and signatureKey are specified, requests can match either. In other words, requests that match one of the whitelisted hosts don't necessarily need to be signed, though they can be. ### Default Base URL ### Typically, remote images to be proxied are specified as absolute URLs. However, if you commonly proxy images from a single source, you can provide a base URL and then specify remote images relative to that base. Try it out by running: imageproxy -baseURL https://octodex.github.com/ Then load the codercat image, specified as a URL relative to that base: . Note that this is not an effective method to mask the true source of the images being proxied; it is trivial to discover the base URL being used. Even when a base URL is specified, you can always provide the absolute URL of the image to be proxied. ### Scaling beyond original size ### By default, the imageproxy won't scale images beyond their original size. However, you can use the `scaleUp` command-line flag to allow this to happen: imageproxy -scaleUp true ### WebP support ### Imageproxy can proxy remote webp images, but they will be served in either jpeg or png format (this is because the golang webp library only supports webp decoding) if any transformation is requested. If no format is specified, imageproxy will use jpeg by default. If no transformation is requested (for example, if you are just using imageproxy as an SSL proxy) then the original webp image will be served as-is without any format conversion. Run `imageproxy -help` for a complete list of flags the command accepts. If you want to use a different caching implementation, it's probably easiest to just make a copy of `cmd/imageproxy/main.go` and customize it to fit your needs... it's a very simple command. ## Deploying ## You can build and deploy imageproxy using any standard go toolchain, but here's how I do it. I use [goxc](https://github.com/laher/goxc) to build and deploy to an Ubuntu server. I have a `$GOPATH/willnorris.com/go/imageproxy/.goxc.local.json` file which limits builds to 64-bit linux: ``` json { "ConfigVersion": "0.9", "BuildConstraints": "linux,amd64" } ``` I then run `goxc` which compiles the static binary and creates a deb package at `build/0.2.1/imageproxy_0.2.1_amd64.deb` (or whatever the current version is). I copy this file to my server and install it using `sudo dpkg -i imageproxy_0.2.1_amd64.deb`, which is installed to `/usr/bin/imageproxy`. Ubuntu uses upstart to manage services, so I copy [`etc/imageproxy.conf`](etc/imageproxy.conf) to `/etc/init/imageproxy.conf` on my server and start it using `sudo service imageproxy start`. You will certainly want to modify that upstart script to suit your desired configuration. ### Heroku ### It's easy to vendorize the dependencies with `Godep` and deploy to Heroku. Take a look at [this GitHub repo](https://github.com/oreillymedia/prototype-imageproxy) ### Docker ### A docker image is available at [`willnorris/imageproxy`](https://registry.hub.docker.com/u/willnorris/imageproxy/dockerfile/). You can run it by ``` docker run -p 8080:8080 willnorris/imageproxy -addr 0.0.0.0:8080 ``` Or in your Dockerfile: ``` ENTRYPOINT ["/go/bin/imageproxy", "-addr 0.0.0.0:8080"] ``` ### nginx ### You can use follow config to prevent URL overwritting: ``` location ~ ^/api/imageproxy/ { # pattern match to capture the original URL to prevent URL # canonicalization, which would strip double slashes if ($request_uri ~ "/api/imageproxy/(.+)") { set $path $1; rewrite .* /$path break; } proxy_pass http://localhost:8080; } ``` ## License ## imageproxy is copyright Google, but is not an official Google product. It is available under the [Apache 2.0 License](./LICENSE).