In an example, an apparatus comprises processing circuitry, the processing circuitry comprising: memory, to store a two-dimensional pixel representation of a layer of an object to be made in an additive manufacturing process and pixel information, the pixel information specifying pixels representing a surface of the object and colour for the pixels representing the surface; and an image processor, to generate a downscaled representation of the layer and to process the downscaled representation to propagate colour from pixels representing the surface of the object in the downscaled representation to neighbouring pixels representing an interior of the object in the downscaled representation.