Parameters

mask=corners

You can change the image to a rounded corner shape.

Example) ?mask=corners

corner-radius

You can specify the corner radius in pixels when mask=corners is set.

Example: ?mask=corners&corner-radius=10

mask=ellipse

You can change the image to an elliptical shape.
If the height and width are the same, it will be a circle.

Example) ?mask=ellipse