Image_url

Template: {% image_url output_to_template = entity.image %}
Output: "http://domain.com/path/to/img.jpg"

Template: {% capture imageCode %}thumb-{{size}} border-{{bordercolor}}{% endcapture %}
{% image_url img_path output_to_template = img extension:"png" preset:"transparent20" preset:"border10" imageCode %}
Output: "http://domain.com/path/to/altered/img.jpg"

Template: {% image_url img_path = page.banner_image name:"home-banner" preset:"banner-size" preset:"sepia-simple" %}
<a href="{{img_path}}"><img src="{{img_path}}" class="thumb" /></a>
Output: <a href="http://domain.com/path/to/altered/img.jpg"><img src="http://domain.com/path/to/altered/img.jpg" class="thumb" /></a>