1. A display controller, comprising: a blending stage to blend multiple image layers into one display output image, the blending stage comprising having a plurality of input channels for receiving pixel data for the multiple image layers and multiple blenders for combining the pixel data received by at least two input channels of the plurality of input channels; and a controllable switch to couple an output of at least one blender of the multiple blenders to a display output of the blending stage for regular on-the-fly blending in response to a first condition, and to an offline blending memory for storing a result of an offline blending task in response to a second condition, a blending controller coupled to the blending stage, for controlling operation of the blending stage, and the blending controller having an input to receive layer data describing one or more of locations and properties of the multiple image layers, and a predictor to, based on the layer data, predict an availability of the at least one blender, the blending controller further being operative to control the blending stage to perform the offline blending task in dependence of the predicted availability, and to control said controllable switch accordingly.