Description

Image proxy server based on spring cloud gateway filters provides opportunity to modify images on fly.
There are two ways to customize response image:

• By passing additional query parameter at the request, see tables below
• By setting up default filters parameters at the spring application properties

It is available to use several filters for a specific url and enable an image filter by customizing settings of proxied server response (see io.github.aptushkin.proxy.image.modify.predicate.ImageModifierPredicate and responseHeaderName property).

Usage:

1. As standalone http (https in todo list) proxy server to modify image responses from proxied servers
2. As dependency, it is possible to fetch proxy-image-starter to get image modifications filters for your custom spring cloud gateway server
3. TODO: As part of spring cloud microservices infrastructure (eureka, config server)
4. TODO: As part of your Spring REST API server by fetching a starter

How to use inside your spring-cloud-gateway server

Fetch dependency from https://repo1.maven.org/maven2:
Maven:

<dependency>
    <groupId>io.github.artemptushkin.proxy.image</groupId>
    <artifactId>proxy-image-starter</artifactId>
    <version>1.0.3</version>
</dependency>

Gradle:

compile group: 'io.github.aptushkin.proxy.image', name: 'proxy-image-starter', version: '0.0.1-SNAPSHOT'

Use spring properties to activate custom image filters:

proxy.image:
    enalbed: true

Customization of gateway filters properties

1. Enable default filter to proxy every request to the target destination

   spring:
     cloud:
       gateway:
         default-filters:
           - ProxyForward
   

2. Customize routing properties to specify image modification filters

    spring.cloud.gateway.routes:
      - id: modify_image_router
      uri: no://op
       predicates:
        - Path=/**

3. Specify required filters

   spring.cloud.gateway:
    filters:
      name: ModifyImageSize
      args:
        responseHeaderName: Content-Type
        regexp: image/.*

Available image filters

Resize filter

Spring properties name: ResizeImage

Default properties:

Property	Required	Description
defaultWidth	N	Default width value of resize method
defaultHeight	N	Default height value of resize method
defaultMode	N	Default mode value of resize method; See http://javadox.com/org.imgscalr/imgscalr-lib/4.2/org/imgscalr/Scalr.Mode.html
defaultMethod	N	Default method value of resize method; http://javadox.com/org.imgscalr/imgscalr-lib/4.2/org/imgscalr/Scalr.Method.html
responseHeaderName	Y	The header name of proxied server response
regexp	Y	Regex to verify response header value. If matched then current filter should be applied
onNotExistedHeader	N	If true, current filter will be applied; otherwise not
defaultFormat	N	default file format for image modification

Query parameters:

Property	Description
width	Width value of target image
height	Height value of target image
format	File format for image modification
mode	Mode value of resize method; See http://javadox.com/org.imgscalr/imgscalr-lib/4.2/org/imgscalr/Scalr.Mode.html
method	Method value of resize method; See http://javadox.com/org.imgscalr/imgscalr-lib/4.2/org/imgscalr/Scalr.Mode.html

Curl example:

curl --location --request GET 'http://github.githubassets.com/images/modules/open_graph/github-octocat.png?width=100&height=300&format=jpg'

Crop filter

Spring properties name: CropImage

Default properties:

Property	Required	Description
defaultWidth	N	Default width value of crop method
defaultHeight	N	Default height value of crop method
defaultX	N	Default X value of crop method; Used to crop the proxy image from the top-left corner
defaultY	N	Default Y value of crop method; Used to crop the proxy image from the top-left corner
responseHeaderName	Y	The header name of proxied server response
regexp	Y	Regex to verify response header value. If matched then current filter should be applied
onNotExistedHeader	N	If true, current filter will be applied; otherwise not
defaultFormat	N	default file format for image modification

Query parameters:

Property	Description
width	Width value of target image
height	Height value of target image
format	File format for image modification
x	X value of crop method; Used to crop the proxy image from the top-left corner
y	Y value of crop method; Used to crop the proxy image from the top-left corner

Curl example:

curl --location --request GET 'http://github.githubassets.com/images/modules/open_graph/github-octocat.png?width=600&height=500&x=400&y=100&format=jpg'

Rotate filter

Spring properties name: RotateImage

Default properties:

Property	Required	Description
rotation	N	Default rotation value for rotation method; See http://javadox.com/org.imgscalr/imgscalr-lib/4.2/org/imgscalr/Scalr.Rotation.html
responseHeaderName	Y	The header name of proxied server response
regexp	Y	Regex to verify response header value. If matched then current filter should be applied
onNotExistedHeader	N	If true, current filter will be applied; otherwise not
defaultFormat	N	default file format for image modification

Query parameters:

Property	Description
rotation	Rotation value for rotation method; See http://javadox.com/org.imgscalr/imgscalr-lib/4.2/org/imgscalr/Scalr.Rotation.html
format	File format for image modification

Curl example:

curl --location --request GET 'http://github.githubassets.com/images/modules/open_graph/github-octocat.png?rotation=CW_180'

Development

How to build

mvn clean install

How to run

Run proxy server with classpath config file

java -jar ./proxy-image-server/target/proxy-image-server-0.0.1-SNAPSHOT.jar

How deploy current build to sonartype nexus

mvn clean deploy

How to release deploy to sonartype nexus

mvn clean release:prepare release:perform -Prelease

TODO

1. Enabled HTTPS proxy requests for image-server
2. Make starter for common web applications to use it with internal response filters for a specific url
3. To add dependencies of spring cloud infrastructure: eureka-client, config-client