sizing="cover"expands the image to cover all of its specified size.
sizing="contain"expands the image to fit within its specified size.
--iron-image-widthproperty to set the width of the image wrapped by the
--iron-image-heightproperty to set the height of the image wrapped by the
preloadattribute shows a placeholder element in front of the image before it has loaded. Use the
--iron-image-placeholderCSS mixin to style it.
fadeattribute, the placeholder element is hidden with no transition when the image loads.
fadeattribute, the placeholder element is fades away when the image loads.
placeholderattribute to specify a background image for the placeholder element.