# imageproxy # imageproxy is a caching image proxy server written in golang. It supports dynamic image resizing and URL whitelisting. This project was inspired by, and is designed to be an alternative to, WordPress's [photon service][photon]. Photon is a great free service, but is limited to sites hosted on WordPress.com, or that use the [Jetpack plugin][jetpack]. If you don't want to use Jetpack, then you're asked to use a different service. If you're looking for an alternative hosted service, I'd recommend [resize.ly][], [embed.ly][], or [cloudinary][]. I decided to try building my own for fun. [photon]: http://developer.wordpress.com/docs/photon/ [jetpack]: http://jetpack.me/ [resize.ly]: https://resize.ly/ [embed.ly]: http://embed.ly/display [cloudinary]: http://cloudinary.com/ ## URL Structure ## imageproxy URLs are of the form `http://localhost/{options}/{remote_url}`. ### Options ### Options are specified as a comma delimited list of parameters, which can be supplied in any order. Duplicate parameters overwrite previous values. The format is a superset of [resize.ly's options](https://resize.ly/#demo). #### Size #### The size option takes the general form `{width}x{height}`, where width and height are numbers. Integer values greater than 1 are interpreted as exact pixel values. Floats between 0 and 1 are interpreted as percentages of the original image size. If either value is omitted or set to 0, it will be automatically set to preserve the aspect ratio based on the other dimension. If a single number is provided (with no "x" separator), it will be used for both height and width. #### Crop Mode #### Depending on the options specified, an image may be cropped to fit the requested size. In all cases, the original aspect ratio of the image will be preserved; imageproxy will never stretch the original image. When no explicit crop mode is specified, the following rules are followed: - If both width and height values are specified, the image will be scaled to fill the space, cropping if necessary to fit the exact dimension. - If only one of the width or height values is specified, the image will be resized to fit the specified dimension, scaling the other dimension as needed to maintain the aspect ratio. If the `fit` option is specified together with a width and height value, the image will be resized to fit within a containing box of the specified size. As always, the original aspect ratio will be preserved. Specifying the `fit` option with only one of either width or height does the same thing as if `fit` had not been specified. #### Rotate #### The `r{degrees}` option will rotate the image the specified number of degrees, counter-clockwise. Valid degrees values are `90`, `180`, and `270`. Images are rotated **after** being resized. #### Quality #### The `q{percentage}` option can be used to specify the output quality (JPEG only). #### Flip #### The `fv` option will flip the image vertically. The `fh` option will flip the image horizontally. Images are flipped **after** being resized and rotated. ### 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 | 200x 0.15x | 15% original width, proportional height | 0.15x x100 | 100px tall, proportional width | x100 100x150 | 100 by 150 pixels, cropping as needed | 100x150 100 | 100px square, cropping as needed | 100 150,fit | scale to fit 150px square, no cropping | 150,fit 100,r90 | 100px square, rotated 90 degrees | 100,r90 100,fv,fh | 100px square, flipped horizontal and vertical | 100,fv,fh 200x,q60 | 200px wide, proportional height, 60% quality | 200x,q60 ## Getting Started ## Install the package using: go get willnorris.com/go/imageproxy Once installed, change directories to `$GOPATH/willnorris.com/go/imageproxy` and run the proxy using: go run cmd/imageproxy/main.go This will start the proxy on port 8080, without any caching and with no host whitelist (meaning any remote URL can be proxied). Test this by navigating to and you should see a 500px square coder octocat. ### Disk cache ### By default, the imageproxy command uses an in-memory cache that will grow unbounded. To cache images on disk instead, include the `cacheDir` flag: go run cmd/imageproxy/main.go -cacheDir /tmp/imageproxy Reload the [codercat URL](http://localhost:8080/500/https://octodex.github.com/images/codercat.jpg), and then inspect the contents of `/tmp/imageproxy`. There should be two files there, one for the original full-size codercat image, and one for the resized 500px version. ### Host whitelist ### You can limit the remote hosts that the proxy will fetch images from using the `whitelist` flag. This is useful, for example, for locking the proxy down to your own hosts to prevent others from abusing it. Of course if you want to support fetching from any host, leave off the whitelist flag. Try it out by running: go run cmd/imageproxy/main.go -whitelist example.com Reload the [codercat URL](http://localhost:8080/500/https://octodex.github.com/images/codercat.jpg), and you should now get an error message. You can specify multiple hosts as a comma separated list, or prefix a host value with `*.` to allow all sub-domains as well. Run `go run cmd/imageproxy/main.go -help` for a complete list of flags the command accepts. If you want to use a different caching implementation, it's probably easiest to just make a copy of `cmd/imageproxy/main.go` and customize it to fit your needs... it's a very simple command. ## Deploying ## You can build and deploy imageproxy using any standard go toolchain, but here's how I do it. I use [goxc](https://github.com/laher/goxc) to build and deploy to an Ubuntu server. I have a `$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. ## License ## This application is distributed under the Apache 2.0 license found in the [LICENSE](./LICENSE) file.