Last week, I described how to add a dynamic watermark to your images on the JVM. I didn’t find any library, so I had to develop the feature, or, more precisely, an embryo of a feature, by myself. Depending on your tech stack, you must search for an existing library or roll up your sleeves. For example, Rust offers such an out-of-the-box library. Worse, this approach might be impossible to implement if you don’t have access to the source image.
Another alternative is to use ready-made components, namely imgproxy and Apache APISIX. I already combined them to resize images on-the-fly.
Here’s the general sequence flow of the process:
- When APISIX receives a specific pattern, it calls
imgproxywith the relevant parameters imgproxyfetches the original image and the watermark to apply- It watermarks the original image and returns the result to APISIX
Let’s say the pattern is /watermark/*.
We can define two routes:
routes:
- uri: "*" (1)
upstream:
nodes:
"server:3000": 1
- uri: /watermark/* (2)
plugins:
proxy-rewrite: (3)
regex_uri:
- /watermark/(.*)
- /dummy_sig/watermark:0.8:nowe:20:20:0.2/plain/http://server:3000/$1 (4)
upstream:
nodes:
"imgproxy:8080": 1 (5)| 1 | Catch-all route that forwards to the web server |
| 2 | Watermark images route |
| 3 | Rewrite the URL… |
| 4 | …with an imgproxy-configured route and… |
| 5 | …forward to imageproxy |
You can find the exact rewritten URL syntax in imgproxy documentation. The watermark itself is configured via a single environment variable. You should buy `imgproxy’s Pro version if you need different watermarks. As a poor man’s alternative, you could also set up different instances, each with its watermark, and configure APISIX to route the request to the desired instance.
In this post, we implemented a watermarking feature with the help of imgproxy.
The more I think about it, the more I think they make a match made in Heaven.