check_metadata.yml

name: Image metadata check CI

on:
  push:
    branches: [master]
  pull_request:
    paths:
      - '**.webp'
      - '**.png'
      - '**.jpg'
  
jobs:
  build:
    name: Ubuntu - Image Metadata
    runs-on: ubuntu-latest
    
    permissions:
      contents: read
      pull-requests: write

    steps:
      - name: exiftool installation
        run: |
          sudo apt-get install --assume-yes exiftool

      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
          # this makes the HEAD be the last commit on the PR, not the merge commit, so wrong older commits would get buried
          # ref: ${{ github.event.pull_request.head.sha }}

      - name: PR env setup
        if: ${{ github.event_name == 'pull_request' }}
        env:
          # figured this out from here: https://docs.github.com/en/webhooks/webhook-events-and-payloads?actionType=edited#pull_request
          SHA: ${{ github.event.pull_request.head.sha }}
          BASE_SHA: ${{ github.event.pull_request.base.sha }}
        run: echo SHA is $SHA

      - name: push env setup
        if: ${{ github.event_name == 'push' }}
        env:
          SHA: ${{ github.event.push.after }}
          BASE_SHA: ${{ github.event.push.before }}
        run: echo SHA is $SHA

      - name: read/export image metadata
        # -id: image_check
        run: |
          mapfile -t image_files < <(git diff --name-only ${BASE_SHA} ${SHA} | grep '\.webp$')

          git status
          # array of accepted copyright strings
          accepted_cr=("GNU GPL v2+|CC BY-SA 4.0|CC0")
          # cycle through the changed image files, make sure they have the right fields
          for file in "${image_files[@]}"; do
            # check -Artist tag, fail if missing
            artist="$(exiftool -Artist $file)"
            artist="${artist#*: }"
            if [ -z "$artist" ] ; then
              echo "no Artist EXIF tag in $file"
              exit 1
            else
              echo "Artist tag in $file is $artist"
            fi
            # check -Copyright tag, fail if missing or wrong type
            copyright="$(exiftool -Copyright $file)"
            copyright="${copyright#*: }"
            if [ -z "$copyright" ] ; then
              echo "no Copyright EXIF tag in $file"
              exit 1
            # elif [[ ( "$copyright" != ${accepted_cr[0]} ) && ( "$copyright" != ${accepted_cr[1]}) ]] ; then
            elif [[ ! "|${accepted_cr[*]}|" =~ "|${copyright}|" ]]; then
              echo "$copyright is not an accepted license"
              exit 1
            else
              echo "Copyright tag in $file is $copyright"
            fi
          done
#      - name: The image_check step has failed
#        if: ${{ failure() && steps.image_check.conclusion == 'failure' }}