Rounding the corners of the splash screen image according to the theme's //roundness// preference.
The rounding of the splash screen //block// itself depends on the `wcol_menu_back.roundness` theme settings, and user can even set it to zero.
So, in this case the splash //image// rounding will not match the //block// ones.
This patch allows you to add proper corner rounding when the image is displayed.
It process only the corner part of the image, both corners in one pass, so a small number of operations are performed.
It also makes it easier to create new splash images as there is no need to worry about adding corner rounding.
Splash screen screenshots:
{F8339092, width=680}