Encoding and decoding an image may be performed by setting a plurality of segments of a second color component block based on pixel values of a first color component block. ; supplying air into combustion chamber at two levels during afterburning step: prechamber pyrogas air supply level, and an upper part of combustion chamber air supply level; and quenching an off-gas to 200-250\xb0 C. 970 gcm3, and an I21 value of less than 20 dgmin; characterized in that the polyethylene composition extrudes at an advantageously high specific throughput at an advantageously low melt temperature, and wherein the film has a gel count of less than 100.