1. A method of image processing comprising altering an input image using a non-linear image transform to generate an output image, the process comprising correcting an image on an area-by-area basis to generate an output image intensity (O ij ) of an area which is different to an input image intensity (I ij ) of the area, the output image intensity (O ij ) of an area being related to the input image intensity (I ij ) of the area by the ratio: 
 amplification coefficient= O ij /I ij wherein the image processing method produces an output image in which the amplification coefficient of a given area is varied in dependence upon the amplification coefficient of at least one neighbouring area, in order that that, in at least part of the image, the local contrast of the input image is at least partially preserved in the output image.