python实现图片批量压缩程序

from PIL import Image
import os
import 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 = 1.0
SIZE_small = 1.5
SIZE_more_small = 2.0


def 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 False


def 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_list


def 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,file_list)
    else:
      pass
  else:
    print "source directory not exist!"