A source comprised of a single image.
Build a Source from a set of images with given widths.
A source defined using widths (like 300w).
Build a Source from a set of images with given densities.
A source defined using densities (like 2x).
Set the sizes attribute. The second argument is the (optional) default size.
Image types supported
A source set of images, used to build a
sourcetag.