app/themes/hugo-theme-stack/layouts/partials/helper/image.html

{{ $result := dict "exists" false "permalink" nil "resource" nil "isDefault" false }}
{{ $imageField := default "image" .Context.Site.Params.featuredImageField }}
{{ $imageValue := index .Context.Params $imageField }}

{{ if $imageValue }}
    <!-- If page has `image` field set -->
    {{ $result = merge $result (dict "exists" true) }}
    {{ $url := urls.Parse $imageValue }}

    {{ if or (eq $url.Scheme "http") (eq $url.Scheme "https") }}
        <!-- Is an external image -->
        {{ $result = merge $result (dict "permalink" $imageValue) }}
    {{ else }}
        {{ $pageResourceImage := .Context.Resources.GetMatch (printf "%s" ($imageValue | safeURL)) }}
        
        {{ if $pageResourceImage }}
            <!-- If image is found under page bundle -->
            {{ $result = merge $result (dict "permalink" $pageResourceImage.RelPermalink) }}

            <!-- Disable SVG image processing, not supported by Hugo -->
            {{ if ne (path.Ext $imageValue) ".svg" }}
                {{ $result = merge $result (dict "resource" $pageResourceImage) }}
            {{ end }}
        {{ else }}
            <!-- Can not find the image under page bundle. Could be a relative linked image -->
            {{ $result = merge $result (dict "permalink" (relURL $imageValue)) }}
        {{ end }}

    {{ end }}

{{ else if and (ne .Type nil) (index .Context.Site.Params.defaultImage .Type) }}
    <!-- Type arg is set, check for defaultImage setting -->
    {{ $defaultImageSetting := index .Context.Site.Params.defaultImage .Type }}

    {{ if $defaultImageSetting.enabled }}
        {{ $result = merge $result (dict "isDefault" true) }}
        {{ $result = merge $result (dict "exists" true) }}

        {{ if $defaultImageSetting.local }}
            {{ $siteResourceImage := resources.GetMatch (printf "%s" ($defaultImageSetting.src | safeURL)) }}

            {{ if $siteResourceImage }}
                <!-- Try search image under site's assets folder -->
                {{ $result = merge $result (dict "permalink" $siteResourceImage.RelPermalink) }}
                {{ $result = merge $result (dict "resource" $siteResourceImage) }}
            {{ else }}
                <!-- Can not find the image -->
                {{ errorf "Failed loading image: %q" $defaultImageSetting.src }}
                {{ $result = merge $result (dict "exists" false) }}
            {{ end }}

        {{ else }}
            <!-- External image -->
            {{ $result = merge $result (dict "permalink" (relURL $defaultImageSetting.src)) }}
        {{ end }}
        
    {{ end }}

{{ end }}

{{ return $result }}