Today, if you want to blur a raster image, you have to introduce it into the widget tree and use a BackdropFilter. If you wan tto blur geometry, you have to use a MaskFilter on a paint and paint it on a Canvas.

We should be able to add ImageFilter to Paint (or something like that) so that you can blur raster images when drawing them to a canvas.

See #29483 (comment) for an example of how this gets awkward today.

/cc @apwilson