Canvas - reduced size resizing texture

I can create a Canvas texture which is a fixed size in pixels, and gets stretched as the canvas changes size.
I can create a texture which resizes to fill the canvas.

But what I want is a texture which resizes to be a certain proportion of the canvas size... e.g I create a Canvas 400x400 and a texture 200x200, as I resize the Canvas the texture resizes to retain that 50% scaling.

Is this something I can do using flags to createTexture?