A perfect fit
Use this property to stretch, shrink, or perfectly fit a background image to match the element's size.
Specify one of these keyword values:
|contain||Scale the image to be perfectly contained within the element, preserving its aspect ratio by leaving whitespace in the unfilled area|
|cover||Scale the image to fully cover the element, preserving its aspect ratio by clipping the overflowed area|
Or specify two of these measurement units, one for the width, the other for the height.
|%||Shrink or stretch the image to be a given percentage of the element's width or height|
|px||Shrink or stretch the image to be exactly that many pixels wide or high|
|auto||Determine the amount to shrink or stretch using the other value|
If only one measurement unit is provided, it is used as the rule for fitting the width of the image to the background, keeping the height in its normal aspect ratio.