python实现图片批量压缩程序

from PIL import Imageimport osimport sys# 定义可以识别的图片文件类型，可以自行扩充valid_file_type = ['.jpg', '.png']# 定义压缩比，数值越大，压缩越小SIZE_normal = 1.0SIZE_small = 1.5SIZE_more_small = 2.0def make_directory(directory):  """创建目录"""  os.makedirs(directory)def directory_exists(directory):  """判断目录是否存在"""  if os.path.exists(directory):    return True  else:    return Falsedef list_img_file(directory):  """列出目录下所有文件，并筛选出图片文件列表返回"""  old_list = os.listdir(directory)  # print old_list  new_list = []  for filename in old_list:    if os.path.isfile(filename):      f, e = os.path.splitext(filename)      if e in valid_file_type:        new_list.append(filename)      else:        pass    else:      pass  # print new_list  return new_listdef print_help():  print """  This program helps compress many image files  you can choose which scale you want to compress your img(jpg/png/etc)  1) normal compress(4M to 1M around)  2) small compress(4M to 500K around)  3) smaller compress(4M to 300K around)  """def compress(choose, des_dir, file_list):  """压缩算法，img.thumbnail对图片进行压缩，还可以改变宽高数值进行压缩"""  if choose == '1':    scale = SIZE_normal  if choose == '2':    scale = SIZE_small  if choose == '3':    scale = SIZE_more_small  for infile in file_list:    img = Image.open(infile)    # size_of_file = os.path.getsize(infile)    w, h = img.size    img.thumbnail((int(w/scale), int(h/scale)))    img.save(des_dir + '/' + infile)if __name__ == "__main__":  src_dir, des_dir = sys.argv[1], sys.argv[2]  if directory_exists(src_dir):    if not directory_exists(des_dir):      make_directory(des_dir)    # business logic    file_list = list_img_file(src_dir)    # print file_list    if file_list:      print_help()      choose = raw_input("enter your choice:")      compress(choose, des_dir, file_list)    else:      pass  else:    print "source directory not exist!"