1. An imager system comprising: an imaging array comprising a plurality of pixels; a processor circuit for outputting digital pixel signals representing incident light on the pixels of said array; and a compression circuit for compressing said digital pixel signals by encoding said pixel signals such that sequential pixel signals in each row are each encoded as first and second transmission data determined based upon a plurality of first and second data, wherein: said first data is based on differential pixel signals each determined from a corresponding one of a plurality of sets of sequential pixel signals; said second data is determined based upon at least one categorization of said first data values by predetermined ordered ranges, said second data comprising an ordered sequence of category identifiers by frequency of occurrence within said ranges; said first transmission data being assigned to said pixel signals from a selected codeword data set of a plurality of codeword data sets, said selected codeword data set being selected by matching said second data with one of said plurality of codeword data sets; and said second transmission data is determined for each pixel signal based upon a category identifier assigned to said pixel and a position within said range associated with said category identifier.