pub(crate) fn unpremultiply_rgba(image: &mut RgbaImage)Expand description
Convert premultiplied-alpha RGBA pixels to the straight alpha PNG expects. Every cursor
source feeding the callback stores premultiplied color (XFixes and Xcursor by format
definition, wl_shm/dmabuf by Wayland convention); encoding those values as straight
alpha double-darkens antialiased edges. Rounds as (c * 255 + a/2) / a, clamped —
selkies’ python seed path mirrors this exact integer math so both sources hash a cursor
to the same content handle.