BackgroundSizeStyle

Encode / sanitize value to put inside calc() function

Encode / sanitize value to put inside url() function

This keyword specifies that the background image should be scaled to be as large as possible while ensuring both its dimensions are less than or equal to the corresponding dimensions of the background positioning area. --MDN

This keyword specifies that the background image should be scaled to be as small as possible while ensuring both its dimensions are greater than or equal to the corresponding dimensions of the background positioning area. --MDN

Wrap the provided expression in CSS calc() function.

ch represents the width, or more precisely the advance measure, of the glyph "0" (zero, the Unicode character U+0030) in the element's font. --MDN

em represents the calculated font-size of the element. If used on the font-size property itself, it represents the inherited font-size of the element. --MDN

The inherit CSS keyword causes the element for which it is specified to take the computed value of the property from its parent element. --MDN

The initial CSS keyword applies the initial (or default) value of a property to an element. --MDN

1 pt is 4/3 of a pixel.

Pixels

rem represents the font-size of the root element (typically ). When used within the root element font-size, it represents its initial value (a common browser default is 16px, but user-defined preferences may modify this). --MDN

The revert CSS keyword reverts the cascaded value of the property from its current value to the value the property would have had if no changes had been made by the current style origin to the current element. --MDN

The unset CSS keyword resets a property to its inherited value if the property naturally inherits from its parent, and to its initial value if not. In other words, it behaves like the inherit keyword in the first case, when the property is an inherited property, and like the initial keyword in the second case, when the property is a non-inherited property. --MDN

1 vh is equal to 1% of the height of the viewport's initial containing block --MDN

1 vmax is equal to the larger of 1 vw and 1 vh --MDN

1 vmin is equal to the smaller of 1 vw and 1 vh --MDN

1 vw is equal to 1% of the width of the viewport's initial containing block --MDN