{{- /*
Open Graph image for link previews. The theme's head/meta.html writes og:image only for the
"image" param; without it, this uses the first image in the page, a Markdown image or a
gallery-image shortcode, scaled down to at most 1200 pixels wide, with its alt text as
og:image:alt.
*/ -}}
{{- if not ($.Param "image") -}}
  {{- /* Whichever comes first: a Markdown image or a gallery-image shortcode (src and alt in "…" or `…`). */ -}}
  {{- with findRESubmatch `!\[([^\]]*)\]\(\s*<?([^\s)>]+)|\{\{<\s*gallery-image\s([^}]*)>\}\}` .RawContent 1 -}}
    {{- $alt := index . 0 1 -}}
    {{- $dest := index . 0 2 -}}
    {{- with index . 0 3 -}}
      {{- $dest = "" -}}
      {{- $alt = "" -}}
      {{- with findRESubmatch "\\bsrc=(?:\"([^\"]*)\"|`([^`]*)`)" . 1 }}{{ $dest = or (index . 0 1) (index . 0 2) }}{{ end -}}
      {{- with findRESubmatch "\\balt=(?:\"([^\"]*)\"|`([^`]*)`)" . 1 }}{{ $alt = or (index . 0 1) (index . 0 2) }}{{ end -}}
    {{- end -}}
    {{- $url := "" -}}
    {{- $width := 0 -}}
    {{- $height := 0 -}}
    {{- $resource := false -}}
    {{- if findRE `^https?://` $dest -}}
      {{- $url = $dest -}}
    {{- else -}}
      {{- $resource = or ($.Resources.Get (strings.TrimPrefix "./" $dest)) (resources.Get $dest) -}}
    {{- end -}}
    {{- with $resource -}}
      {{- $image := . -}}
      {{- if and (eq .ResourceType "image") (ne .MediaType.SubType "svg") -}}
        {{- /* Turned as its EXIF orientation says; Hugo doesn't do that when it resizes. */ -}}
        {{- $image = .Filter images.AutoOrient -}}
        {{- if gt $image.Width 1200 }}{{ $image = $image.Resize "1200x" }}{{ end -}}
        {{- $width = $image.Width -}}
        {{- $height = $image.Height -}}
      {{- end -}}
      {{- $url = $image.Permalink -}}
    {{- end -}}
    {{- with $url }}
<meta property="og:image" content="{{ . }}">
{{- with $width }}
<meta property="og:image:width" content="{{ . }}">
<meta property="og:image:height" content="{{ $height }}">
{{- end }}
{{- with $alt }}
<meta property="og:image:alt" content="{{ . }}">
{{- end }}
<meta name="twitter:card" content="summary_large_image">
    {{- end -}}
  {{- end -}}
{{- end -}}