1. A system comprising: a memory configured to store target luminance values; and an image data processor configured to: for one or more blocks of an image: determine one or more tone adjustment values that, when applied to both a representation of a distribution of luminance values for a block and to representations of distributions of luminance values for one or more neighboring blocks, generate luminance values for both the block and the one or more neighboring blocks that match or approximate corresponding luminance values of the target luminance values; and perform the one or more tone adjustments on the image according to the one or more tone adjustment values.