Grayscale and binary image data compression

Arrangements 202 and procedures 400 for compressing grayscale, binary and bi-level image data 114 are disclosed. With respect to compressing binary and bi-level image data, individual byte image data values are retained 510, 508 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 508-1, 508-2 for bytes in a current byte row 102 with replacement data strings 302. The replacement data strings 302 include a replacement positioning code 310 and a replacement count code 304 for replicating retained byte image data values for subsequent data decompression as a group of substantially identical byte values.