As far as image encoders go, do we really need 2 parameters to describe compression parameters, bitrate and resolution? Why not just have bitrate, where you can

As far as image encoders go, do we really need 2 parameters to describe compression parameters, bitrate and resolution? Why not just have bitrate, where you can decompress an image to an arbitrary resolution because the encoding is not tied to resolution? For example, you could have a representation f(w,x,y) where x and y are the (floating point) pixel coordinates you want to decompress, and w is the compressed image representation. You can of course optimise this so you don't need to run f() as many times as many pixels you want to get out of w. With some neural network based codec of the future this should be possible, and I hope image (and video/audio) codecs get there at some point.