便宜VPS测评
有时候图片太大了占内存很烦，本来手机内存也就那么点，放一个图片稍微大一点的，都不能放一个成百上千张，这不是很烦嘛。于是，这又让我来灵感了，既然图片给了我难题，那么我就来接受这样的挑战。所以，我决定用python来试试可不可以压缩图片，居然一试就成功了，分享出来给大家。
dynamic_quality.py
import PIL.Image
from math import log
from SSIM_PIL import compare_ssim
# pip install SSIM-PIL
from PIL import ImageFile
ImageFile.LOAD_TRUNCATED_IMAGES = True
def get_ssim_at_quality(photo, quality):
"""
Return the ssim for this JPEG image saved at the specified quality
"""
ssim_photo = "tmp.jpg"
# optimize is omitted here as it doesn't affect
# quality but requires additional memory and cpu
photo.save(ssim_photo, format="JPEG", quality=quality, progressive=True)
ssim_score = compare_ssim(photo, PIL.Image.open(ssim_photo))
return ssim_score
def _ssim_iteration_count(lo, hi):
"""
Return the depth of the binary search tree for this range
"""
if lo >= hi:
return 0
else:
return int(log(hi - lo, 2)) + 1
def jpeg_dynamic_quality(original_photo):
"""
Return an integer representing the quality that this JPEG image should be
saved at to attain the quality threshold specified for this photo class.
Args:
original_photo - a prepared PIL JPEG image (only JPEG is supported)
"""
ssim_goal = 0.9 #the original value is 0.95
hi = 35 #the original value is 85
lo = 30 #the original value is 80
# working on a smaller size image doesn't give worse results but is faster
# changing this value requires updating the calculated thresholds
photo = original_photo.resize((200, 200))
# if not _should_use_dynamic_quality():
# default_ssim = get_ssim_at_quality(photo, hi)
# return hi, default_ssim
# 95 is the highest useful value for JPEG. Higher values cause different behavior
# Used to establish the image's intrinsic ssim without encoder artifacts normalized_ssim = get_ssim_at_quality(photo, 10)
selected_quality = selected_ssim = None
# loop bisection. ssim function increases monotonically so this will converge for i in range(_ssim_iteration_count(lo, hi)):
curr_quality = (lo + hi) // 2
curr_ssim = get_ssim_at_quality(photo, curr_quality)
ssim_ratio = curr_ssim / normalized_ssim
if ssim_ratio >= ssim_goal:
# continue to check whether a lower quality level also exceeds the goal selected_quality = curr_quality
selected_ssim = curr_ssim
hi = curr_quality
else:
lo = curr_quality
if selected_quality:
return selected_quality, selected_ssim
else:
default_ssim = get_ssim_at_quality(photo, hi)
return hi, default_ssim
test.py
from PIL
import Image
from dynamic_quality import *
def compress(filename,originpath,targetpath):
name = filename.rstrip('.png').rstrip('.jpg')
im = Image.open(originpath+filename)
# print(im.format,im.size,im.mode)
im = im.convert('RGB')
im.format = "JPEG"
new_photo = im.copy()
new_photo.thumbnail(im.size,resample=Image.ANTIALIAS)
save_args = {'format':im.format}
# print(save_args)
# if im.format=='JPEG':
# save_args['quality']=20 save_args['quality'],value=jpeg_dynamic_quality(im) save_args['optimize']=True
save_args['progressive=True']=True
# print("JPEG Quality Changed")
# elif im.format=='PNG':
# save_args['format']='JPEG'
# save_args['quality']=5
# print("PNG Quality Changed") new_photo.save(targetpath+name+".jpg",**save_args)
if __name__ == '__main__':
import os
originpath = "D:\\images\\img\\"
# 需要压缩图片路径 targetpath = "D:\\images\\dangdang_image\\"
# 压缩完图片路径 for root, dirs, files in os.walk(originpath):
for file in files:
compress(file,originpath,targetpath)
