Arrangements and procedures for compressing grayscale, binary and bi-level image data are disclosed. With respect to compressing binary and bi-level image data, individual byte image data values are retained that are different from a same row byte that is n-bytes back. For each retained byte image data value, individual byte image data values are encoded for bytes in a current byte row with replacement data strings. The replacement data strings include a replacement positioning code and a replacement count code for replicating retained byte image data values for subsequent data decompression as a group of substantially identical byte values.