在爬完网上一篇帖子，并得到其中的所有图片链接后，写一个GUI来实现在线预览是一个很自然的想法， 相当于实现一个python版的图片浏览器， 通过这个练习，可以让我们更熟悉PyQt这个库。

这里我用的是PyQt4。

以下是我的写的程序，可以实现以下几个功能。

预览图片：

实现鼠标左键单击即可下翻至下一张图片，鼠标右键单击则是返回前一张图片。

利用本地Cache来解决反复读取的问题。 比如说对同样的两张图片我们想来回比较，我们没必要每次都重新下载。我们可以将图片保存到本地，当以后调用同一张图片时，直接从本地读取缓存来加速。如果我们不想让外界看到缓存的图片，则可以对其进行加密 (尚未实现)。

对动图gif的支持。普通的 jpg 和 Png 格式，利用QLable 即可以显示，但是对于gif，我们则必须利用QMovie来让其动起来。

由于我刚接触这个库，仍然在学习，所以写的不妥或者冗余的地方，希望大家指出。

# coding=utf-8

import sys

import pycurl

import os

import time

from StringIO import StringIO

import re

from PyQt4 import QtGui,QtCore

from PyQt4.QtGui import *

from PyQt4.QtCore import *

# class definition

class Pic_Label(QtGui.QLabel):

def __init__(self):

super(Pic_Label,self).__init__()

self.setFrameStyle(QtGui.QFrame.StyledPanel)

self.cache_map={}

def paintEvent(self, event):

if self.extention !="gif":

size = self.size()

painter = QtGui.QPainter(self)

point = QtCore.QPoint(0,0)

scaledPix = self.pixmap.scaled(size, Qt.KeepAspectRatio, transformMode = Qt.SmoothTransformation)

# start painting the label from left upper corner

point.setX((size.width() - scaledPix.width())/2)

point.setY((size.height() - scaledPix.height())/2)

#print point.x(), ' ', point.y()

painter.drawPixmap(point, scaledPix)

else:

QLabel.paintEvent(self, event)

def mouseReleaseEvent(self,ev):

#self.emit(SIGNAL('clicked()'))

if ev.button() == Qt.RightButton:

self.emit(SIGNAL("RightClick"))

else:

self.emit(SIGNAL("LeftClick"))

def set_image(self,pic_url,index):

if (index in self.cache_map) == False:

self.cache_map[index]=False

self.pixmap = QtGui.QPixmap()

self.retrieve_from_url_cache(pic_url,index)

def retrieve_from_url_cache(self,pic_url,index):

try:

self.extention=re.search(r"\.(\w+)$", pic_url).group(1)

except:

self.extention="jpg"

cache_pic_name="Pic_"+str(index)+"."+self.extention

cache_pic_path=os.getcwd()+"\Cache_Pic\\"+cache_pic_name

if self.cache_map[index]==True:

if self.extention =="gif":

movie = QtGui.QMovie(cache_pic_path)

self.setMovie(movie)

movie.start()

else:

#print "Cached!" + cache_pic_path

if self.pixmap.load(cache_pic_path) == False:

#print "use jpg to try again"

if self.pixmap.load(cache_pic_path)== False:

#last resort, try again

self.retrieve_from_url(pic_url,index,cache_pic_path)

self.setPixmap(self.pixmap) # udpate immediately

else:

if self.extention =="gif":

data=self.retrieve_from_url(pic_url,index,cache_pic_path)

self.pixmap.loadFromData(data)

f = open(cache_pic_path, 'wb')

f.write(data)

f.close()

movie = QtGui.QMovie(cache_pic_path)

self.setMovie(movie)

movie.start()

else:

data=self.retrieve_from_url(pic_url,index,cache_pic_path)

self.pixmap.loadFromData(data)

self.pixmap.save(cache_pic_path)

self.setPixmap(self.pixmap) # udpate immediately

def retrieve_from_url(self,pic_url,index,file_path):

c = pycurl.Curl()

c.setopt(pycurl.PROXY, 'http://192.168.87.15:8080')

c.setopt(pycurl.PROXYUSERPWD, 'LL66269:')

c.setopt(pycurl.PROXYAUTH, pycurl.HTTPAUTH_NTLM)

buffer = StringIO()

c.setopt(pycurl.URL, pic_url)

c.setopt(c.WRITEDATA, buffer)

c.perform()

c.close()

data = buffer.getvalue()

self.cache_map[index]=True

return data

def setMovie(self,movie):

QLabel.setMovie(self, movie)

s=movie.currentImage().size()

self._movieWidth = s.width()

self._movieHeight = s.height()

class Example(QtGui.QWidget):

def __init__(self,thread_url_list):

super(Example, self).__init__()

self.url_list=thread_url_list

self.current_pic_index=0

cwd = os.getcwd()

#print cwd

directory=cwd+"\Cache_Pic"

#print directory

if not os.path.exists(directory):

os.makedirs(directory)

self.initUI()

# making subfolderss to cache pictures

def initUI(self):

layout = QtGui.QGridLayout()

self.label = Pic_Label()

self.label.set_image(self.url_list[0],0)

#self.label = QLabel()

#movie = QtGui.QMovie("Cache_Pic/Pic_0.gif")

#self.label.setMovie(movie)

#movie.start()

layout.addWidget(self.label)

layout.setRowStretch(0,1)

layout.setColumnStretch(0,1)

#self.connect(self.label,SIGNAL('clicked()'),self.fun_next)

self.connect(self.label,SIGNAL("LeftClick"),self.fun_next)

self.connect(self.label,SIGNAL("RightClick"),self.fun_prev)

#b1=QtGui.QPushButton("next")

#b2=QtGui.QPushButton("prev")

#b1.clicked.connect(self.fun_next)

#b2.clicked.connect(self.fun_prev)

#layout.addWidget(b1)

#layout.addWidget(b2)

self.setLayout(layout)

self.setGeometry(300, 300, 500, 500)

self.setWindowTitle('Picture Viewer')

self.show()

# Connect button to image updating

def fun_next(self):

if self.current_pic_index < len(self.url_list)-1:

self.current_pic_index=self.current_pic_index+1

else:

self.current_pic_index=0

self.label.set_image(self.url_list[self.current_pic_index],self.current_pic_index)

sys.stdout.write('\r')

sys.stdout.write("[ %d ] out of (%d)" % (self.current_pic_index+1,len(self.url_list)))

sys.stdout.flush()

def fun_prev(self):

if self.current_pic_index > 0:

self.current_pic_index=self.current_pic_index-1

else:

self.current_pic_index=len(self.url_list)-1

self.label.set_image(self.url_list[self.current_pic_index],self.current_pic_index)

sys.stdout.write('\r')

sys.stdout.write("[ %d ] out of (%d)" % (self.current_pic_index+1,len(self.url_list)))

sys.stdout.flush()

def view_image():

url_list=['https://i.imgur.com/waprhO3.gif','http://static.cnbetacdn.com/article/2017/0831/7f11d5ec94fa123.png','http://static.cnbetacdn.com/article/2017/0831/1b6595175fb5486.jpg']

viewer_app = QtGui.QApplication(sys.argv)

ex = Example(url_list)

sys.exit(viewer_app.exec_())

view_image()