run-length encoding

A string coding compression technique used in facsimile machines to digitize and compress a document prior to transmission by identifying color redundancy in the original document. The transmitting machine scans a document from top-to-bottom and left-to-right, sensing dots of black and white, grayscale, or color at an interval that depends on the resolution setting. Rather than transmitting a set of bits identifying the value of each dot of each line, the scanning machine looks for redundancy, i.e., strings or runs, of dots of the same value.The machine then can transmit a set of bits identifying that value and the length of the run before the value changes. Modified Huffman (MH) is a run-length encoding compression technique used in Group III facsimile machines. See also compression, facsimile, Group III, MH, resolution, and string coding.