|
|
- #!/usr/bin/env python3
- #
- # RunLength decoder (Adobe version) implementation based on PDF Reference
- # version 1.4 section 3.3.4.
- #
- # * public domain *
- #
-
- import sys
-
- def rldecode(data):
- """
- RunLength decoder (Adobe version) implementation based on PDF Reference
- version 1.4 section 3.3.4:
- 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 257 - length
- (2 to 128) times during decompression. A length value of 128
- denotes EOD.
- """
- decoded = []
- i=0
- while i < len(data):
- #print "data[%d]=:%d:" % (i,ord(data[i]))
- length = ord(data[i])
- if length == 128:
- break
- if length >= 0 and length < 128:
- run = data[i+1:(i+1)+(length+1)]
- #print "length=%d, run=%s" % (length+1,run)
- decoded.append(run)
- i = (i+1) + (length+1)
- if length > 128:
- run = data[i+1]*(257-length)
- #print "length=%d, run=%s" % (257-length,run)
- decoded.append(run)
- i = (i+1) + 1
- return ''.join(decoded)
|
