Dynamic image resizing server
The image server is configured through a config.clj file which is passed as argument. The sample configuration shown below can be found in the repository sample-config.clj.
(defconfig
:http {:port 8080}
:vhosts [["localhost"
"127.0.0.1"] (resizer :secret "verysecret"
:watermarks (filesource :basedir "/path/to/my/watermarks")
:source (s3source :bucket "bucketname"
:cred {:endpoint "<endpoint goes here>"
; example https://s3-eu-west-1.amazonaws.com
:access-key "<access key goes here>"
:secret-key "<secret key goes here>"})
:cache (filecache :basedir "/var/lib/imgcache"))
["some.other.domain.tld"
"some.alias.domain.tld"] (resizer :secret "alsoverysecret"
:source (httpsource :url "http://u.r.l/basepath/"
:rewrite {:fromregex #"^([0-9a-zA-Z]{160})\.jpg$"
:replacement "/medias/ignore.jpg?context=$1"})
:cache (s3cache :bucket "cache"
:cred {:endpoint "<endpoint goes here>"
; example https://s3-eu-west-1.amazonaws.com
:access-key "<access key goes here>"
:secret-key "<secret key goes here>"}))])The configuration file has 2 global keys. :http specifies the port the server will be listening on. The :vhosts key is an vector containing all the virtual hosts of the server. Every virtual host definition is in the format [alias1 alias2 alias3] (resizer <resizerconfiguration>.
The resizer is configured with a :secret which is used to validate the checksum. Then a resizer needs a :source :watermarks :cache. A :source is used as a source of images that need to be resized. The :watermarks option is given a source to the location of the watermarks. A :cache in its turn is used to write the resized images to. When a request for a resized images is found in the cache, the cached result is returned.
Currently there are 3 types of sources and 2 types of caches. The sources can both be used for the :source and :watermarks option.
(filesource :basedir "/path/to/images")(s3source :bucket "bucketname"
:cred {:endpoint "<endpoint goes here>"
; example https://s3-eu-west-1.amazonaws.com
:access-key "<access key goes here>"
:secret-key "<secret key goes here>"})(httpsource :url "http://u.r.l/basepath/"
:rewrite {:fromregex #"^([0-9a-zA-Z]{160})\.jpg$"
:replacement "/medias/ignore.jpg?context=$1"})The :rewrite option can be used to rewrite the path of the original image as seen by the imageresizer to another path on the http endpoint.
(s3cache :bucket "bucketname"
:cred {:endpoint "<endpoint goes here>"
; example https://s3-eu-west-1.amazonaws.com
:access-key "<access key goes here>"
:secret-key "<secret key goes here>"})(filecache :basedir "/var/lib/imgcache")java -jar imageresizer-${VERSION}.jar -c config.clj
The basic api url structure for the image resizer is http://hostname:port/checksum/key1/value1/key2/value2/originalimagename
The checksum is calculated as
md5sum (secretkey + 'key1/value1/key2/value2/originalimagename')
The secretkey should match the :secret from the virtual host definition you're using. All mismatching checksums are rejected with a http status 400. This prevents malicious users of generating many variants of a specific image and eating up your precious resources. The originalimagename parameter is the path relative to the configured store of the original image name.
Next you can specify multiple resize operations in the form of key/value pairs.
| key | value | description |
|---|---|---|
| watermark | $(anchor)-watermarkref.ext | Adds a watermark image with reference watermarkref to the image. This watermarkref is resolved from the :watermarks source given in the configuration. Anchor can be one of topleft, topcenter, topright, midleft, midcenter, midright, bottomleft, bottomcenter, bottomright |
| watermark |
|
Same as above, but instead of using an anchor, add the topleft corner of the watermark image to location xoffset,yoffset in the baseimage. |
| crop |
|
This crops the image starting from xoffset,yoffset from the top left corner of the images and cuts out a picture of width x height pixels. |
| size | $(size) | this resizes the image by keeping the aspect ratio and size will be used as the longest edge |
| size | $(size)w | this resizes the image by keeping the aspect ratio and size will be used as the width |
| size | $(size)h | this resizes the image by keeping the aspect ratio and size will be used as the height |
| size |
|
this resizes the image to the given dimensions of width x height. This crops the images from the center so to change the aspect ratio |
| size |
|
this resizes the images to the given dimensions of width x height but instead of cropping from the center it pads the border with a color with rgb value rgbcolor to match the new aspect ratio. |
| output | png | write as png output |
| output | jpg | write to jpg with default quality 90 |
| output | jpg-$(quality) | write to jpg with quality. |
| expires | $(timestamp) | if a link is accessed after timestamp a 404 is generated. If it is accessed before normal processing applies. However the Cache-Control headers and Expires headers are calculated relatively to the expiration timestamp. The timestamp is in milliseconds since epoch. |
The operations can be combined in multiple key value pairs. Check the unit tests for [examples] (../master/test/net/umask/imageresizer/resizer_test.clj#L61) of urls.
Copyright © 2015 Jo Geraerts