BaseJpegDecode.py
JPEGのHuffman decodeのテスト。
#!/usr/bin/env python # coding:utf-8 # BaseJpegDecode.py 2012.9.27 import abc import logging from collections import Counter class BitPattern: def __init__(self, data=0, size=0): self.data = data self.size = size def clear(self): self.data = 0 self.size = 0 def put(self, c, size=8): self.data <<= size self.data |= c self.size += size if self.size > 32: raise ValueError('over flow 32bit') def peek(self, size): return self.data >> (self.size-size) def get(self, size): r = self.peek(size) self.size -= size self.data &= (1<<self.size)-1 return r def match(self, b): if b.size > self.size: return False return self.peek(b.size) == b.peek(b.size) class Huff: def __init__(self, run, value_size, code): self.run = run self.value_size = value_size self.code = code class HuffmanDecode(object): def __init__(self): self._ht = {} def _ht_clear(self, tc, th): self._ht[(tc,th)] = [] def _ht_append(self, tc, th, huff): self._ht[(tc,th)].append(huff) def inputDHT(self, buf): pos = 0 while pos < len(buf): uc = ord(buf[pos]) pos += 1 tc = uc >> 4 th = uc & 0x0f self._ht_clear(tc, th) l_pos = pos pos += 16 code = 0x0000 for i in range(16): l = ord(buf[l_pos + i]) for k in range(l): value = ord(buf[pos]) run = value >> 4; value_size = value & 0x0f h = Huff(run, value_size, BitPattern(code, i+1)) self._ht_append(tc, th, h) pos += 1 code += 1 code <<= 1 def Lookup(self, tc, th, bitpat): for h in self._ht[(tc,th)]: if h.code.size > bitpat.size: return None if bitpat.match(h.code): return h return None def getValue(self, huff, bitpat): value = bitpat.get(huff.value_size) if huff.value_size == 0: return 0 if value & (1<<(huff.value_size-1)): return value value -= (1<<huff.value_size)-1 return value class BaseJpegDecode(object): __metaclass__ = abc.ABCMeta def __init__(self): self._hd = HuffmanDecode() self._seq = 0 self._bitpat = BitPattern() @abc.abstractmethod def outputDC(self, mcu, block, value): pass @abc.abstractmethod def outputAC(self, mcu, block, scan, value): pass @abc.abstractmethod def outputMARK(self, c): pass def _inputScan(self, c): self._bitpat.put(ord(c)) while self._bitpat.size > 0: if self._scan == 0: tc = 0 # DC else: tc = 1 # AC if self._block <= 3: th = 0 else: th = 1 if self._huff == None: self._huff = self._hd.Lookup(tc, th, self._bitpat) if self._huff == None: break self._bitpat.get(self._huff.code.size) # skip code if self._huff.value_size > self._bitpat.size: break value = self._hd.getValue(self._huff, self._bitpat) if self._scan == 0: value += self._old_DC_value[th] self.outputDC(self._mcu, self._block, value) self._old_DC_value[th] = value self._scan += 1 else: if self._huff.run == 0 and self._huff.value_size == 0: self._scan = 64 else: for i in range(self._huff.run): self.outputAC(self._mcu, self._block, self._scan, 0) self._scan += 1 self.outputAC(self._mcu, self._block, self._scan, value) self._scan += 1 if self._scan >= 64: self._scan = 0 self._block += 1 if self._block >= 6: self._block = 0 self._mcu += 1 self._huff = None def input(self, c): if self._seq == 0: if c == '\xff': self._seq += 1 elif self._seq == 1: self.outputMARK(c) if c in '\xd8\xd9\x00': # SOI EOI self._seq = 0 else: self._mark = c self._seq += 1 elif self._seq == 2: self._skip = ord(c) << 8 self._seq += 1 elif self._seq == 3: self._skip += ord(c) self._skip -= 2 self._buf = "" self._seq += 1 elif self._seq == 4: self._buf += c self._skip -= 1 if self._skip > 0: return if self._mark == '\xc4': # DHT self._hd.inputDHT(self._buf) if self._mark == '\xda': # SOS self._mcu = 0 self._block = 0 self._scan = 0 self._old_DC_value = Counter() self._bitpat.clear() self._huff = None self._seq += 1 else: self._seq = 0 elif self._seq == 5: if c == '\xff': self._seq += 1 else: self._inputScan(c) elif self._seq == 6: if c == '\x00': self._inputScan('\xff') self._seq -= 1 else: self.outputMARK(c) self._seq = 0 if __name__ == "__main__": #logging.basicConfig(level=logging.INFO) class DemoJpeg(BaseJpegDecode): def __init__(self, width=160): super(DemoJpeg, self).__init__() self._width = width def clear(self): self._seq = 0 def outputDC(self, mcu, block, value): if block == 0: self._value = 0 if block <= 3: self._value += (value+512) if block == 3: print("%02X" % (self._value/16)), if (mcu % (self._width/16)) == (self._width/16)-1: print "" def outputAC(self, mcu, block, scan, value): pass def outputMARK(self, c): print("MARK: %02X" % ord(c)) import argparse parser = argparse.ArgumentParser() parser.add_argument('-w', '--width', type=int, default=160) parser.add_argument('infiles', nargs='*') args = parser.parse_args() jpeg = DemoJpeg(args.width) for filename in args.infiles: with open(filename, "rb") as f: data = f.read() print("%s %d" % (filename, len(data))) jpeg.clear() for c in data: jpeg.input(c)
