Start Marker | JFIF Marker | Header Length | Identifier
 
0xff, 0xd8  | 0xff, 0xe0 |  2-bytes  | "JFIF\0"

def is_jpg(filename):
  data = open(filename,'rb').read(11)
  if data[:4] != '\xff\xd8\xff\xe0' and data[:4]!='\xff\xd8\xff\xe1': 
    return False
  if data[6:] != 'JFIF\0' and data[6:] != 'Exif\0': 
    return False
  return True

from PIL import Image
def is_jpg(filename):
  try:
    i=Image.open(filename)
    return i.format =='JPEG'
  except IOError:
    return Fals

#coding=utf-8
#summary: 判断图片的有效性
import io
import os
 
from PIL import Image
#判断文件是否为有效（完整）的图片
#输入参数为文件路径
#会出现漏检的情况
def IsValidImage(pathfile):
 bValid = True
 try:
  Image.open(pathfile).verify()
 except:
  bValid = False
 return bValid
 
 
def is_valid_jpg(jpg_file): 
  """判断JPG文件下载是否完整 
  """ 
  if jpg_file.split('.')[-1].lower() == 'jpg': 
    with open(jpg_file, 'rb') as f: 
      f.seek(-2, 2) 
      return f.read() == '\xff\xd9' #判定jpg是否包含结束字段 
  else: 
    return True
 
#利用PIL库进行jpeg格式判定，但有些没有结束字段的文件检测不出来
def is_jpg(filename):
  try:
    i=Image.open(filename)
    return i.format =='JPEG'
  except IOError:
    return False
 
allfiles=os.listdir('image')
log_file=open('img_lossinfo.txt','w')
log = open('img_r.txt','w')
log_w=open('img_w.txt','w')
log1=open('img_jpeg.txt','w')
log2=open('img_notjpg.txt','w')
for i in allfiles:
#if 1:
	if i[-4:]=='.jpg':
		f=os.path.join('image',i)
		value=IsValidImage(f)
		if not value:
			log_file.write(i+'\n')
		if is_valid_jpg(f):
			print f
			log.write(i+'\n')
		else:
			log_w.write(i+'\n')
		if is_jpg(f):
			log1.write(i+'\n')
		else:
			log2.write(i+'\n')