Python读取图片属性信息的实现方法

# -*- coding:utf-8 -*-
import binascii

class ParseMethod(object):
  @staticmethod
  def parse_default(f, count, offset):
    pass

  @staticmethod
  def parse_latitude(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)

    latitude = [0,0,0]
    for i in xrange(count):
      byte = f.read(4)
      numerator = byte.encode('hex')

      byte = f.read(4)
      denominator = byte.encode('hex')

      latitude[i] = float(int(numerator, 16)) / int(denominator, 16)


    print 'Latitude:\t%.2f %.2f\' %.2f\"' % (latitude[0], latitude[1], latitude[2])
    f.seek(old_pos)  


  @staticmethod
  def parse_longtitude(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)

    longtitude = [0,0,0]
    for i in xrange(count):
      byte = f.read(4)
      numerator = byte.encode('hex')

      byte = f.read(4)
      denominator = byte.encode('hex')

      longtitude[i] = float(int(numerator, 16)) / int(denominator, 16)


    print 'Longtitude:\t%.2f %.2f\' %.2f\"' % (longtitude[0], longtitude[1], longtitude[2])
    f.seek(old_pos) 

  @staticmethod
  def parse_make(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)
    byte = f.read(count)
    a = byte.encode('hex')
    print 'Make:\t\t' + binascii.a2b_hex(a)
    f.seek(old_pos) 

  @staticmethod
  def parse_model(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)
    byte = f.read(count)
    a = byte.encode('hex')
    print 'Model:\t\t' + binascii.a2b_hex(a)
    f.seek(old_pos)     

  @staticmethod
  def parse_datetime(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)
    byte = f.read(count)
    a = byte.encode('hex')
    print 'DateTime:\t' + binascii.a2b_hex(a)
    f.seek(old_pos)

  # rational data type, 05
  @staticmethod
  def parse_xresolution(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)

    byte = f.read(4)
    numerator = byte.encode('hex')
    byte = f.read(4)
    denominator = byte.encode('hex')
    xre = int(numerator, 16) / int(denominator, 16)

    print 'XResolution:\t' + str(xre) + ' dpi'
    f.seek(old_pos)

  @staticmethod
  def parse_yresolution(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)

    byte = f.read(4)
    numerator = byte.encode('hex')
    byte = f.read(4)
    denominator = byte.encode('hex')
    xre = int(numerator, 16) / int(denominator, 16)

    print 'YResolution:\t' + str(xre) + ' dpi'
    f.seek(old_pos)

  @staticmethod
  def parse_exif_ifd(f, count, offset):
    old_pos = f.tell()
    f.seek(12 + offset)

    byte = f.read(2)
    a = byte.encode('hex')    
    exif_ifd_number = int(a, 16)

    for i in xrange(exif_ifd_number):
      byte = f.read(2)
      tag_id = byte.encode('hex')
      #print tag_id,

      byte = f.read(2)
      type_n = byte.encode('hex')
      #print type_n,

      byte = f.read(4)
      count = byte.encode('hex')
      #print count,

      byte = f.read(4)
      value_offset = byte.encode('hex')
      #print value_offset

      value_offset = int(value_offset, 16)
      EXIF_IFD_DICT.get(tag_id, ParseMethod.parse_default)(f, count, value_offset)

    f.seek(old_pos)  

  @staticmethod
  def parse_x_pixel(f, count, value):
    print 'X Pixels:\t' + str(value)

  @staticmethod
  def parse_y_pixel(f, count, value):
    print 'y Pixels:\t' + str(value)

  @staticmethod
  def parse_gps_ifd(f, count, offset):
    old_pos = f.tell()    
    f.seek(12 + offset)
    byte = f.read(2)
    a = byte.encode('hex')  
    gps_ifd_number = int(a, 16)

    for i in xrange(gps_ifd_number):
      byte = f.read(2)
      tag_id = byte.encode('hex')
      #print tag_id,

      byte = f.read(2)
      type_n = byte.encode('hex')
      #print type_n,

      byte = f.read(4)
      count = byte.encode('hex')
      #print count,

      byte = f.read(4)
      value_offset = byte.encode('hex')
      #print value_offset

      count = int(count, 16)
      value_offset = int(value_offset, 16)
      GPS_IFD_DICT.get(tag_id, ParseMethod.parse_default)(f, count, value_offset)

    f.seek(old_pos) 

IFD_dict = {
  '010f' : ParseMethod.parse_make ,
  '0110' : ParseMethod.parse_model ,
  '0132' : ParseMethod.parse_datetime ,
  '011a' : ParseMethod.parse_xresolution ,
  '011b' : ParseMethod.parse_yresolution ,
  '8769' : ParseMethod.parse_exif_ifd ,
  '8825' : ParseMethod.parse_gps_ifd
}

EXIF_IFD_DICT = {
  'a002' : ParseMethod.parse_x_pixel ,
  'a003' : ParseMethod.parse_y_pixel
}

GPS_IFD_DICT = {
  '0002' : ParseMethod.parse_latitude ,
  '0004' : ParseMethod.parse_longtitude
}


with open('image.jpg', 'rb') as f:
  byte = f.read(2)
  a = byte.encode('hex')
  print 'SOI Marker:\t' + a

  byte = f.read(2)
  a = byte.encode('hex')
  print 'APP1 Marker:\t' + a

  byte = f.read(2)
  a = byte.encode('hex')
  print 'APP1 Length:\t' + str(int(a, 16)) + ' .Dec'

  byte = f.read(4)
  a = byte.encode('hex')
  print 'Identifier:\t' + binascii.a2b_hex(a)

  byte = f.read(2)
  a = byte.encode('hex')
  print 'Pad:\t\t' + a 

  print 

  print 'Begin to print Header.... '
  print 'APP1 Body: '

  byte = f.read(2)
  a = byte.encode('hex')
  print 'Byte Order:\t' + a  

  byte = f.read(2)
  a = byte.encode('hex')
  print '42:\t\t' + a 

  byte = f.read(4)
  a = byte.encode('hex')
  print '0th IFD Offset:\t' + a 

  print 'Finish print Header'

  print 'Begin to print 0th IFD....'
  print
  #print 'Total: ',
  byte = f.read(2)
  a = byte.encode('hex')
  interoperability_number = int(a, 16)
  #print interoperability_number


  for i in xrange(interoperability_number):
    byte = f.read(2)
    tag_id = byte.encode('hex')
    #print tag_id,

    byte = f.read(2)
    type_n = byte.encode('hex')
    #print type_n,

    byte = f.read(4)
    count = byte.encode('hex')
    #print count,

    byte = f.read(4)
    value_offset = byte.encode('hex')
    #print value_offset

    count = int(count, 16)
    value_offset = int(value_offset, 16)

    # simulate switch
    IFD_dict.get(tag_id, ParseMethod.parse_default)(f, count, value_offset)


  print
  print 'Finish print 0th IFD....'