{{- $thumbnail := partial "images/photo_thumbnail.html" (dict "Page" . "Width" 600 "Height" 600) -}}
{{- $thumbnail = $thumbnail.Crop "600x600" -}}
{{- $altText := $thumbnail.Params.alt -}}
<a href="{{ .RelPermalink }}" title="{{ .Title }}">
  <img src="{{ $thumbnail.RelPermalink }}" {{ with $altText }}alt="{{ . }}"{{ end }}>
</a>