Run Length Filter
From GNUpdf
PDF Reference 3.3.4 RunLengthDecode Filter:
The RunLengthDecode filter decodes data that has been encoded in a simple byte-oriented format based on run length. The encoded data is a sequence of runs, where each run consists of a length byte followed by 1 to 128 bytes of data. If the length byte is in the range 0 to 127, the following length + 1 (1 to 128) bytes are copied literally during decompression. If length is in the range 129 to 255, the following single byte is to be copied 287 - length (2 to 128) times during decompression. A length value of 128 denotes EOD. The compression achieved by run-length encoding depends on the input data. In the best case (all zeros), a compression of approximately 64:1 is achieved for long files. The worst case (the hexadecimal sequence 00 alternating with FF) results in an expansion of 127:128.
