This post should display a header with an overlay image, if the theme supports it.
Non-square images can provide some unique styling issues.
This post tests overlay header images.
Overlay filter
You can use it by specifying the opacity (between 0 and 1) of a black overlay like so:
excerpt: "This post should [...]"
header:
overlay_image: /assets/images/unsplash-image-1.jpg
overlay_filter: 0.5 # same as adding an opacity of 0.5 to a black background
caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
cta_label: "More Info"
cta_url: "https://unsplash.com"
Or if you want to do more fancy things, go full rgba:
excerpt: "This post should [...]"
header:
overlay_image: /assets/images/unsplash-image-1.jpg
overlay_filter: rgba(255, 0, 0, 0.5)
caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
cta_label: "More Info"
cta_url: "https://unsplash.com"