Optimize Images in a Pull Request with GitHub Actions

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Published on August 31st, 2020
By Armno P.

GitHub Actions is a service that provides automation and CI/CD built into GitHub’s interface and runs on GitHub’s infrastructure or our own servers.

It’s pretty similar to GitLab CI to GitLab or Azure Pipelines to Azure DevOps. The workflows and configurations look more similar to Azure Pipelines than GitLab CI in my opinion.

A Use Case for GitHub Actions: Image Optimization

One thing that can be (and should be) automated is image optimization: to reduce images file size to make them load and display faster.

We can use a GitHub Actions to make sure images that are on the master branch, will always be optimized before they get deployed to the live website.

In this post, I will use Image Actions to automatically optimize images in this blog when a pull request is created. Normally I do this task manually using tinypng.com for every single blog post.

Adding Image Actions to the Project

Go to repo page on GitHub, select Actions menu and select ‘set up a workflow yourself’.

Actions page on GitHub repo

It brings us to the workflow editor page. Here we will have to create a yml file to define tasks for the automation we need.

Workflow editor page

To create a new workflow using the Image Action, we can either:

Search for Image Actions

We can add some extra options and quality settings of each file type under with: section of the step.

My workflow looks like this:

name: Compress images

      - "**.jpg"
      - "**.jpeg"
      - "**.png"
      - "**.webp"
    name: calibreapp/image-actions
    runs-on: ubuntu-latest
      - name: Checkout Repo
        uses: actions/checkout@master

      - name: Compress Images
        uses: calibreapp/image-actions@master
          githubToken: ${{ secrets.GITHUB_TOKEN }}
          jpegQuality: "70"
          jpegProgressive: true
          pngQuality: "70"

When we save the workflow, it creates a new yaml file and put in the repo. On the Actions page, now there should be a new workflow created.

Workflow is create on the Actions page

Next I create a test pull request to add 2 new images in my /uses page. There is a new check created.

A new pull request is created

We can go to the details page to see it runs.

Action details

On the first run, the workflow scans and optimizes all images in the repo so it takes a while. But in the end, it reduces images by 37.7% or 21.59 MB from the repo. It is clear that many images are not properly optimized for a long time!

With Netlify’s Deploy Previews feature, I can compare original images and optimized images side-by-side.

Comparing original and optimized images

Back to the pull request view, the Actions adds a new commit and push back to the branch.

new commit created by github actions

It also creates a new comment with optimization results into the pull request.

Results of image optimization is added into the pull request

Some images are already optimized, so they are skipped.

Some images are already optimized

Comparing results with TinyPNG

Tinypng.com is an online image optimization service I usually use. It can still do a better job than the Image Actions in terms of producing smaller file size.

Comparing results with images optimized by tinypng.com
Comparing results - Top: Image Actions. Bottom: tinypng.com


The Image Actions is a good addition to my workflow. Although it doesn’t produce the smallest file size of the images, but what I get back is an automated workflow and I don’t have to manually optimize images again when writing a blog post.

Another thing I like about GitHub Actions is the marketplace: there are plenty actions in various types created by the community and are ready to use.

Happy automating 🦾.

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