#
# JPEGファイルのヘッダ(?)部分を読み込み、画像のサイズを調べる
#
# JPEGファイルのフォーマットは以下のURLを参照のうえ、実際のフ
# ァイル数点をサンプルとした
# http://siisise.net/format.html#JPEG
# http://www.ba.wakwak.com/~tsuruzoh/Computer/Digicams/exif.html
#
# 2002.9.12 Exifファイルに対応

import os
from string import lower

SOI           = 0xFFD8
APP1          = 0xFFE1
EXIF_HDR      = 'Exif\0\0'
TIFF_TAG_MARK = 0x002A

type2bytes = {  # TIFFタグのデータ形式
   1: 1,  # unsigned byte
   2: 1,  # ascii string
   3: 2,  # unsigned short
   4: 4,  # unsigned long
   5: 8,  # unsigned rational (分数:unsigned longが2つ、分子・分母の順)
   6: 1,  # signed byte
   7: 1,  # undefined
   8: 2,  # signed short
   9: 4,  # signed long
  10: 8,  # signed ratuonal (分数:signed longが2つ、分子・分母の順)
  11: 4,  # single float
  12: 8   # double float
} 

IFD_TAG = {
  # IFD0タグ
  0x010e: 'ImageDescription',
  0x010f: 'Make',
  0x0110: 'Model',
  0x0112: 'Orientation',
  0x011a: 'XResolution',
  0x011b: 'YResolution',
  0x0128: 'ResolutionUnit',
  0x0131: 'Software',
  0x0132: 'DateTime',
  0x013e: 'WhitePoint',
  0x013f: 'PrimaryChromaticities',
  0x0211: 'YCbCrCoefficients',
  0x0213: 'YCbCrPositioning',
  0x0214: 'ReferenceBlackWhite',
  0x8298: 'Copyright',
  0x8769: 'ExifIFDPointer',

  # SubIFDタグ
  0x829a: 'ExposureTime',
  0x829d: 'FNumber',
  0x8822: 'ExposureProgram',
  0x8827: 'ISOSpeedRatings',
  0x9000: 'ExifVersion',
  0x9003: 'DateTimeOriginal',
  0x9004: 'DateTimeDigitized',
  0x9101: 'ComponentsConfiguration',
  0x9102: 'CompressedBitsPerPixel',
  0x9201: 'ShutterSpeedValue',
  0x9202: 'ApertureValue',
  0x9203: 'BrightnessValue',
  0x9204: 'ExposureBiasValue',
  0x9205: 'MaxApertureValue',
  0x9206: 'SubjectDistance',
  0x9207: 'MeteringMode',
  0x9208: 'LightSource',
  0x9209: 'Flash',
  0x920a: 'FocalLength',
  0x927c: 'MakerNote',
  0x9286: 'UserComment',
  0x9290: 'SubsecTime',
  0x9291: 'SubsecTimeOriginal',
  0x9292: 'SubsecTimeDigitized',
  0xa000: 'FlashPixVersion',
  0xa001: 'ColorSpace',
  0xa002: 'ExifImageWidth',
  0xa003: 'ExifImageHeight',
  0xa004: 'RelatedSoundFile',
  0xa005: 'InteroperabilityIFDPointer',
  0xa20e: 'FocalPlaneXResolution',
  0xa20f: 'FocalPlaneYResolution',
  0xa210: 'FocalPlaneResolutionUnit',
  0xa215: 'ExposureIndex',
  0xa217: 'SensingMethod',
  0xa300: 'FileSource',
  0xa301: 'SceneType',
  0xa302: 'CFAPattern',

  # InteroperabilityIFDタグ
  0x0001: 'InteroperabilityIndex',
  0x0002: 'InteroperabilityVersion',
  0x1000: 'RelatedImageFileFormat',
  0x1001: 'RelatedImageWidth',
  0x1002: 'RelatedImageLength',

  # IFD1タグ
  0x0100: 'ImageWidth',
  0x0101: 'ImageLength',
  0x0102: 'BitsPerSample',
  0x0103: 'Compression',
  0x0106: 'PhotometricInterpretation',
  0x0111: 'StripOffsets',
  0x0112: 'Orientation',
  0x0115: 'SamplesPerPixel',
  0x0116: 'RowsPerStrip',
  0x0117: 'StripByteConunts',
  0x011a: 'XResolution',
  0x011b: 'YResolution',
  0x011c: 'PlanarConfiguration',
  0x0128: 'ResolutionUnit',
  0x0201: 'JpegInterchangeFormat',
  0x0202: 'JpegInterchangeFormatLength',
  0x0211: 'YCbCrCoefficients',
  0x0212: 'YCbCrSubSampling',
  0x0213: 'YCbCrPositioning',
  0x0214: 'ReferenceBlackWhite',
  0x00fe: 'NewSubfileType',

  # その他のタグ
  0x00ff: 'SubfileType',
  0x012d: 'TransferFunction',
  0x013b: 'Artist',
  0x013d: 'Predictor',
  0x013e: 'WhitePoint',
  0x013f: 'PrimaryChromaticities',
  0x0142: 'TileWidth',
  0x0143: 'TileLength',
  0x0144: 'TileOffsets',
  0x0145: 'TileByteCounts',
  0x014a: 'SubIFDs',
  0x015b: 'JPEGTables',
  0x828d: 'CFARepeatPatternDim',
  0x828e: 'CFAPattern',
  0x828f: 'BatteryLevel',
  0x83bb: 'IPTC/NAA',
  0x8773: 'InterColorProfile',
  0x8824: 'SpectralSensitivity',
  0x8825: 'GPSInfo',
  0x8828: 'OECF',
  0x8829: 'Interlace',
  0x882a: 'TimeZoneOffset',
  0x882b: 'SelfTimerMode',
  0x920b: 'FlashEnergy',
  0x920c: 'SpatialFrequencyResponse',
  0x920d: 'Noise',
  0x9211: 'ImageNumber',
  0x9212: 'SecurityClassification',
  0x9213: 'ImageHistory',
  0x9214: 'SubjectLocation',
  0x9215: 'ExposureIndex',
  0x9216: 'TIFF/EPStandardID',
  0x9290: 'SubSecTime',
  0x9291: 'SubSecTimeOriginal',
  0x9292: 'SubSecTimeDigitized',
  0xa20b: 'FlashEnergy',
  0xa20c: 'SpatialFrequencyResponse',
  0xa214: 'SubjectLocation'

}


class JPG_SZ:
  def __init__(self, filename=None):
    if filename != None:
      self.setFile(filename)
    self.endian = 0  # 0: Motorola, 1:Intel
    self.img_info = {}

  def setFile(self, filename):
    self.jpgfile = filename
    self.ErrMsg = ''
    if not os.access(self.jpgfile, os.R_OK | os.F_OK):
      self.ErrMsg = 'file not found!'
      return 1

  def Read(self):
    data = open(self.jpgfile, 'rb').read(20000)  # 20kB読めば充分？
    start = 0
    end = 2
    marker = self.bin2int(data[start:end])
    if marker != SOI:
      self.ErrMsg = 'Not a JPEG file!'
      return 1

    marker = self.bin2int(data[start+2:end+2])
    if marker == APP1:
      start = end + 2
      ret = self.ReadExifFile(start, data)
    else:
      start = end
      ret = self.ReadJfifFile(start, data)

    return ret

  def ReadJfifFile(self, start, data):
    ret = 0
    end = start + 2
    while 1:
      marker = lower(self.bin2str(data[start:end]))
      if marker == lower('FFE0'):
        sz = self.bin2int(data[end:end+2])
        if data[end+2:end+2+4] != 'JFIF':
          self.ErrMsg = 'Not a JPEG file!'
          ret = 1
          break
        start = end + sz
        end = start + 2
      elif marker == lower('FFDB'):
        start = end + 67
        end = start + 2
      elif marker == lower('FFC4'):
        sz = self.bin2int(data[end:end+2])
        start = end + sz
        end = start + 2
      elif marker == lower('FFC0'):
        sz_y = self.bin2int(data[end+3:end+5])
        sz_x = self.bin2int(data[end+5:end+7])
        self.X, self.Y = (sz_x, sz_y)
        ret = 0
#        start = end + 17
#        end = start + 2
        break
      else:
        if marker[:2] == lower('FF'):
          sz = self.bin2int(data[end:end+2])
          start = end + sz
          end = start + 2
        else:
          break

    return ret

  def ReadExifFile(self, start, data):
    d = self.img_info
    end = start + 2
    sz_app1 = self.bin2int(data[start:end])
    start = end
    end = start + 6
    if data[start:end] != EXIF_HDR:
      self.ErrMsg = 'Not a EXIF file!'
      return 1
    start = end
    end = start + 2
    s = data[start:end]
    if s == 'II':
      self.endian = 1
    elif s == 'MM':
      self.endian = 0
    self.offset_base = start
    start = end
    end = start + 2
    sz = self.bin2int(data[start:end])
    if sz != TIFF_TAG_MARK:
      self.ErrMsg = 'Not a EXIF file!'
      return 1
    start = end
    end = start + 4
    sz = self.bin2int(data[start:end])
#    start = end
    start = self.offset_base + sz
    end = start + 2

    #
    # IFD0の読みとり
    #
    next_ifd_pos = self.readIFD(start, data)
    #
    # SubIFDの読みとり
    #
    start = d['ExifIFDPointer'] + self.offset_base
    p = self.readIFD(start, data)
    while(p != self.offset_base):
      start = p
      p = self.readIFD(start, data)
    #
    # IDF1の読みとり
    #
    start = next_ifd_pos
    p = self.readIFD(start, data)
    #
    # InteroperabilityIFDの読みとり
    if p != self.offset_base:
      start = p
    else:
      if d.has_key('InteroperabilityIFDPointer'):
        start = d['InteroperabilityIFDPointer'] + self.offset_base
      if start != self.offset_base:
        p = self.readIFD(start, data)

    if d.has_key('ExifImageWidth') and d.has_key('ExifImageHeight'):
      self.X, self.Y = d['ExifImageWidth'], d['ExifImageHeight']
    else:
      self.X, self.Y = None, None
    return 0

  def readIFD(self, start, data):
    d = self.img_info
    num_ifd = self.bin2int(data[start:start+2])
    tag_pos = start + 2
    for n in range(num_ifd):
      tag_nam = IFD_TAG[self.bin2int(data[tag_pos:][:2])]
      tagd_typ = self.bin2int(data[tag_pos+2:][:2])
      tagd_siz = self.bin2int(data[tag_pos+4:][:4])
      tagd = data[tag_pos+8:][:4]
      sz = type2bytes[tagd_typ] * tagd_siz
      if sz > 4:
        offset = self.bin2int(tagd)
        tagd = data[self.offset_base+offset:][:sz]

      if tagd_typ in (2, 7):
        d[tag_nam] = tagd
      elif tagd_typ == 5:
        if self.endian == 0:
          d1 = self.bin2int(tagd[:4])
          d2 = self.bin2int(tagd[4:])
        elif self.endian == 1:
          d2 = self.bin2int(tagd[:4])
          d1 = self.bin2int(tagd[4:])
        d[tag_nam] = str(d1) + '/' + str(d2)
      elif tagd_typ == 10:
        if self.endian == 0:
          d1 = self.bin2sint(tagd[:4])
          d2 = self.bin2sint(tagd[4:])
        elif self.endian == 1:
          d2 = self.bin2sint(tagd[:4])
          d1 = self.bin2sint(tagd[4:])
        d[tag_nam] = str(d1) + '/' + str(d2)
      elif tagd_typ in (1, 3, 4):
        d[tag_nam] = self.bin2int(tagd)
      elif tagd_typ in (6, 8, 9):
        d[tag_nam] = self.bin2sint(tagd)

      tag_pos = tag_pos + 12

    next_ifd_pos = self.offset_base + self.bin2int(data[tag_pos:][:4])

    return next_ifd_pos

  def bin2str(self, d):
    s = ''
    for n in d:
      ss = hex(ord(n))[2:]
      if len(ss) == 1:
        ss = '0' + ss
      s = s + ss
    return s

  def bin2int(self, d):
    m = len(d) - 1
    r = 0
    for n in range(len(d)):
      if self.endian == 0:
        r = r + ord(d[n]) * pow(256, m - n)
      elif self.endian == 1:
        r = r + ord(d[n]) * pow(256, n)
    return r

  def bin2sint(self, d):
    m = pow(256, len(d)) / 2
    r = self.bin2int(d)
    if r >= m:
      r = r - m * 2
    return r

  def getResult(self):
    return self.X, self.Y

  def getErrMsg(self):
    return self.ErrMsg

if __name__ == '__main__':
#  filename = '317.jpg'
  filename = 'DSC00494.JPG'
  J = JPG_SZ(filename)
  if J.Read() == 0:
    print '%s: (x, y) = (%d, %d)' % ((filename,) + J.getResult())
  else:
    print J.getErrMsg()