GitHub Action using ImageMagick: Create a PNG and commit it to the repo - github

Question

Background
I'm maintaining a forked repository that contains a LaTeX project. The README.md contains a .png preview of the .pdf compiled from the example .tex file included in the repo. I often forget to update the .png version using the following ImageMagick command:
magick convert -density 1200 -background white -alpha off Twenty-Seconds-Icons_cv.pdf -quality 90 Twenty-Seconds-Icons_cv.png
Thus I would like to automate this process using GitHub Actions.
Workflow
I think the main.yml file should look something like this, however, I don't fully understand what I am doing.
name: PDF to PNG
on:
push:
branches:
- kaspar
pull_request:
branches:
- kaspar
jobs:
build:
runs-on: ubuntu-latest
steps:
- name: Install ImageMagick
run: sudo apt install imagemagick # Seems to work and already be included with ubuntu-latest...
- name: Convert PDF to PNG
run: # How?
- name: Commit the updated PNG
run: # How?
Output:
Run sudo apt install imagemagick
sudo apt install imagemagick
shell: /usr/bin/bash -e {0}
WARNING: apt does not have a stable CLI interface. Use with caution in scripts.
Reading package lists...
Building dependency tree...
Reading state information...
imagemagick is already the newest version (8:6.9.10.23+dfsg-2.1ubuntu11.2).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Questions
It seems like I can just run bash shell commands with run: ; is this true?
How/where can I access the .pdf file in the repo from inside the GitHub Actions Ubuntu machine?
Where should I save the .png file, is there a ~ directory?
How can I commit the .png file generated by ImageMagick to the repo?
Would git commit <file> -m "updated png version of the CV" work?

Answer 1

I figured out a solution to my problem:
I forgot to checkout the repository
ghostscript needed to be installed explicitly
The security policy for ImageMagic needs to be edited for it to process PDFs
On Ubuntu the ImageMagick command doesn’t work for 1200 dpi (900 is ok in my case), on Windows, this works just fine
I found out how to commit and push files
name: PDF to PNG
on:
push:
branches:
- kaspar
pull_request:
branches:
- kaspar
jobs:
build:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout#v2
- name: Install ghostscript
run: sudo apt install ghostscript
- name: Change ImageMagick security policy
run: |
DQT='"'
SRC="rights=${DQT}none${DQT} pattern=${DQT}PDF${DQT}"
RPL="rights=${DQT}read\|write${DQT} pattern=${DQT}PDF${DQT}"
sudo sed -i "s/$SRC/$RPL/" /etc/ImageMagick-6/policy.xml
- name: Convert PDF to PNG
run: convert -density 900 -background white -alpha off Twenty-Seconds-Icons_cv.pdf -quality 90 Twenty-Seconds-Icons_cv.png
- name: Commit PNG
id: commit
run: |
git config --local user.email "action[bot]#github.com"
git config --local user.name "github-actions[bot]"
git add Twenty-Seconds-Icons_cv.png
if [-z "$(git status --porcelain)"]; then
echo "::set-output name=push::false"
else
git commit -m "[bot] updated Twenty-Seconds-Icons_cv.png"
echo "::set-output name=push::true"
fi
shell: bash
- name: Push Commit
if: steps.commit.outputs.push == 'true'
uses: ad-m/github-push-action#master
with:
github_token: ${{ secrets.SECRET_TOKEN }}