fediversity_website/themes/nluug/layouts/_default/_markup/render-image.html

<picture>
  {{ $isJPG := eq (path.Ext .Destination) ".jpg" }}
  {{ $isPNG := eq (path.Ext .Destination) ".png" }}

  {{ if ($isJPG) -}}
    {{ $webpPath:= replace .Destination ".jpg" ".webp" }}
    {{ $webpPathStatic:= printf "static/%s" $webpPath }}

    {{ if (fileExists $webpPathStatic) -}}
      <source srcset="{{ $webpPath | safeURL }}" type="image/webp" >
    {{- end }}
  {{- end }}

  {{ if ($isPNG) -}}
    {{ $webpPath:= replace .Destination ".png" ".webp" }}
    {{ $webpPathStatic:= printf "static/%s" $webpPath }}

    {{ if (fileExists $webpPathStatic) -}}
      <source srcset="{{ $webpPath | safeURL }}" type="image/webp" >
    {{- end }}
  {{- end }}

  {{- $img := .Page.Resources.GetMatch .Destination -}}
  {{- if and (not $img) .Page.File -}}
      {{ $path := path.Join .Page.File.Dir .Destination }}
      {{- $img = resources.Get $path -}}
  {{- end -}}
  <img
    src="{{ .Destination | safeURL }}"
    alt="{{ .Text }}"
    loading="lazy"
    decoding="async"
    width="{{ $img.Width }}"
    height="{{ $img.Height }}"
  />
</picture>