cullmann.io/themes/blowfish/layouts/partials/hero/background.html

{{ $disableImageOptimization := .Page.Site.Params.disableImageOptimization | default false }}

{{- $images := .Resources.ByType "image" -}}
{{- $featured := $images.GetMatch "*background*" -}}
{{- if not $featured }}{{ $featured = $images.GetMatch "*feature*" }}{{ end -}}
{{- if not $featured }}{{ $featured = $images.GetMatch "{*cover*,*thumbnail*}" }}{{ end -}}

{{ if and .Params.featureimage (not $featured) }}
{{- $url:= .Params.featureimage -}}
{{ $featured = resources.GetRemote $url }}
{{ end }}

{{- if not $featured }}
 {{ with .Site.Params.defaultBackgroundImage }}
  {{ if or (strings.HasPrefix . "http:") (strings.HasPrefix . "https:") }}
   {{ $featured = resources.GetRemote . }}
  {{ else }}
   {{ $featured = resources.Get . }}
  {{ end }}
 {{ end }}
{{ end -}}

{{ $isParentList := eq (.Scratch.Get "scope") "list"  }}
{{ $shouldBlur := $.Params.layoutBackgroundBlur | default (or 
        (and ($.Site.Params.article.layoutBackgroundBlur | default true) (not $isParentList)) 
        (and ($.Site.Params.list.layoutBackgroundBlur | default true) ($isParentList))
    ) }}
{{ $shouldAddHeaderSpace := $.Params.layoutBackgroundHeaderSpace | default (or 
        (and ($.Site.Params.article.layoutBackgroundHeaderSpace | default true) (not $isParentList)) 
        (and ($.Site.Params.list.layoutBackgroundHeaderSpace | default true) ($isParentList))
    ) }}
{{- with $featured -}}

{{ if $shouldAddHeaderSpace | default true}}
<div id="hero" class="h-[150px] md:h-[200px]"></div>
{{ end }}

{{ if or $disableImageOptimization (strings.HasSuffix $featured ".svg")}}
    {{ with . }}
    <div class="fixed inset-x-0 top-0 h-[800px] single_hero_background nozoom"
    style="background-image:url({{ .RelPermalink }});">
    {{ end }}
{{ else }}
    {{ with .Resize (print ($.Site.Params.backgroundImageWidth | default "1200") "x") }}
    <div class="fixed inset-x-0 top-0 h-[800px] single_hero_background nozoom"
    style="background-image:url({{ .RelPermalink }});">
    {{ end }}
{{ end }}

    <div class="absolute inset-0 bg-gradient-to-t from-neutral dark:from-neutral-800 to-transparent mix-blend-normal">
    </div>
    <div
        class="absolute inset-0 opacity-60 bg-gradient-to-t from-neutral dark:from-neutral-800 to-neutral-100 dark:to-neutral-800 mix-blend-normal">
    </div>
</div>
{{ if $shouldBlur | default false }}
<div id="background-blur" class="fixed opacity-0 inset-x-0 top-0 h-full single_hero_background nozoom backdrop-blur-2xl"></div>
<script>
    window.addEventListener('scroll', function (e) {
        var scroll = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0;
        var background_blur = document.getElementById('background-blur');
        background_blur.style.opacity = (scroll / 300)
    });
</script>
{{ end }}
{{- end -}}