Kult Resizer

Project Year:



s3 bucket
image resizer
· 2018 ·

Kult Resizer is a simple PHP utility which can be used to resize images coming from an Amazon AWS S3 bucket. The images are resized and served on-the-fly but there's also a caching mechanism in order to optimize performance. It also supports subfolders, up to 1 level. The tool is meant to run as a standalone microservice, however it can also be included in an existing PHP project.


The easiest way to run this locally is with Docker.

First create a file on root level called variables.env

Then put here the environmental variables:

Variable Description
CACHE_FOLDER the name of the directory for the cached images. I recommend to use cache. Anyway, if you need to change it, also make sure you change it in start.sh otherwise the folder will not be created in the Docker container.
BUCKET_URL the URL of your S3 bucket.
DEBUG_MODE when something doesn't work it's difficult to understand what's going on. Set this to 1 to enable debug mode.


CACHE_FOLDER=cache BUCKET_URL=https://s3.eu-central-1.amazonaws.com/atw-images DEBUG_MODE=0

When this is done you can run it:

docker-compose up --build

Kult Resizer at work

Now that the service is running you can see it at work.

Let's assume that you have configured your .ENV file as explained above, and that you have an image in your S3 bucket at this URL:


If you want to retrieve this file, on a resolution of max 400 pixels, just use this link:


This means that the image will be resized in a way that the bigger side will be 400px.

If your file is not in a subfolder, but on the root level of the bucket ( i.e. https://s3.eu-central-1.amazonaws.com/atw-images/logo.jpg ) just omit the folder parameter, like this:


There is also a "contain" feature:


This means that the image will have max. width of 400px and max. height of 200px. The resulting image will be a proportioned image fitting inside these dimensions.


  • Currently only JPGs are supported. PNGs should be supported as well.

  • There is no cropping logic. It might be interesting to introduce a square-crop feature

  • Make debug mode logging less crappy :)

  • Add a way to flush the cache without needing to re-deploy the service or manually delete the cache folder

Antonio Cosentino © 2021 - All rights reserved