1. An image processing system comprising: an input ( 104 ) for receiving image data and depth data defining luminance and/or color for image positions in an image and distance to objects visible at said image positions respectively; a dilator ( 122 ) coupled to the input and configured to dilate the depth data, in a direction to move an edge between a region of image positions with a relatively smaller distance and a region of image positions with a relatively greater distance towards the region of image positions with a relatively greater distance; a compressor ( 120 ) coupled to said input and to an output of the dilator and configured to compress the image data and the dilated depth data.