A system for decoding compressed image data in the form of pixel blocks representing an image of a first resolution to provide an image of a reduced second resolution decompresses a pixel block of the first resolution image. The system involves selecting (204) a sub-set of frequency domain coefficients in the compressed pixel block data, and processing elements (204,205,206,208) of the sub-set of coefficients to provide pixel data representing pixels comprising a spatially distributed sub-set of pixels in the pixel block in the first resolution image and excludes other pixels of the pixel block. The pixel data representing pixels comprising the spatially distributed pixels is formatted (210) to provide the reduced second resolution image.