Video Coding and Decoding Using Compression Control Rules

An image to be encoded is divided into blocks, and image intensity values in at least some blocks are transformed to provide transform coefficients which are quantised with quantisation parameters to derive a compressed bitstream. The encoding comprises selecting a compression control rule (e.g. Intensity Dependent (ID) profile), and for an image area, identifying a compression control parameter (e.g. image intensity for the area), the parameter varying between at least some image areas. Values (e.g. compression of the dynamic range) in the image area are varied in accordance with the rule operating on the control parameter, and the selected rule is signalled in association with the compressed bitstream for use at the decoder. At the decoder, the rule is extracted from the compressed bitstream and - after performing inverse quantisation and an inverse transform to form image values - those image values are inverse scaled.