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1.ImagesPipeline简介
Scrapy用ImagesPipeline类提供一种方便的方式来下载和存储图片。
特点:
2.ImagesPipeline工作流程
当使用图片管道 ImagePipeline,典型的工作流程如下:
3.操作过程
项目目录结构:
要想成功爬取图片,需要经过以下几个步骤:
(1)在items.py中添加image_urls、images和image_paths字段,代码如下:
class DoubanImgsItem(scrapy.Item):
# define the fields for your item here like:
# name = scrapy.Field()
image_urls = Field()
images = Field()
image_paths = Field()
(2)在settings.py中设置条件和属性,代码如下:
# Configure item pipelines
# See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
# ImagePipeline的自定义实现类
ITEM_PIPELINES = {
'douban_imgs.pipelines.DoubanImgDownloadPipeline': 300,
}
#设置图片下载路径
IMAGES_STORE = 'D:\\doubanimgs'
# 过期天数
IMAGES_EXPIRES = 90 #90天内抓取的都不会被重抓
(3)在spiders/download_douban.py中书写ImageSpider的代码:
# coding=utf-8
from scrapy.spiders import Spider
import re
from scrapy import Request
from ..items import DoubanImgsItem
class download_douban(Spider):
name = 'download_douban'
default_headers = {
'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
'Accept-Encoding': 'gzip, deflate, sdch, br',
'Accept-Language': 'zh-CN,zh;q=0.8,en;q=0.6',
'Cache-Control': 'max-age=0',
'Connection': 'keep-alive',
'Host': 'www.douban.com',
'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36',
}
def __init__(self, url='1638835355', *args, **kwargs):
self.allowed_domains = ['douban.com']
self.start_urls = [
'http://www.douban.com/photos/album/%s/' % (url)]
self.url = url
# call the father base function
# super(download_douban, self).__init__(*args, **kwargs)
def start_requests(self):
for url in self.start_urls:
yield Request(url=url, headers=self.default_headers, callback=self.parse)
def parse(self, response):
list_imgs = response.xpath('//div[@class="photolst clearfix"]//img/@src').extract()
if list_imgs:
item = DoubanImgsItem()
item['image_urls'] = list_imgs
yield item
(4)在pipelines.py中自定义ImagePipeline代码:
# -*- coding: utf-8 -*-
# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.html
from scrapy.pipelines.images import ImagesPipeline
from scrapy.exceptions import DropItem
from scrapy import Request
from scrapy import log
class DoubanImgsPipeline(object):
def process_item(self, item, spider):
return item
class DoubanImgDownloadPipeline(ImagesPipeline):
default_headers = {
'accept': 'image/webp,image/*,*/*;q=0.8',
'accept-encoding': 'gzip, deflate, sdch, br',
'accept-language': 'zh-CN,zh;q=0.8,en;q=0.6',
'cookie': 'bid=yQdC/AzTaCw',
'referer': 'https://www.douban.com/photos/photo/2370443040/',
'user-agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36',
}
def get_media_requests(self, item, info):
for image_url in item['image_urls']:
self.default_headers['referer'] = image_url
yield Request(image_url, headers=self.default_headers)
def item_completed(self, results, item, info):
image_paths = [x['path'] for ok, x in results if ok]
if not image_paths:
raise DropItem("Item contains no images")
item['image_paths'] = image_paths
return item
在自定义ImagePipeline代码中,作为重要的是要重载get_media_requests(self, item, info)和item_completed(self, results, item, info)这两个函数。
ImagePipeline根据image_urls中指定的url进行爬取,可以通过get_media_requests为每个url生成一个Request。如:
for image_url in item['image_urls']:
self.default_headers['referer'] = image_url
yield Request(image_url, headers=self.default_headers)
图片下载完毕后,处理结果会以二元组的方式返回给item_completed()函数。这个二元组定义如下:
(success, image_info_or_failure)
其中,第一个元素表示图片是否下载成功;第二个元素是一个字典。如:
def item_completed(self, results, item, info):
image_paths = [x['path'] for ok, x in results if ok]
if not image_paths:
raise DropItem("Item contains no images")
item['image_paths'] = image_paths
return item
4.爬取结果
运行结果如下:
下载成功以后,你就会在刚才设置的保存图片的路径里看到下载完成的图片:IMAGES_STORE = ‘D:\doubanimgs’
5.扩展
默认情况下,使用ImagePipeline组件下载图片的时候,图片名称是以图片URL的SHA1值进行保存的。
如: 图片URL:http://www.example.com/image.jpg SHA1结果:3afec3b4765f8f0a07b78f98c07b83f013567a0a 则图片名称:3afec3b4765f8f0a07b78f98c07b83f013567a0a.jpg
如果想进行更改,请参考:使用scrapy框架的ImagesPipeline下载图片如何保持原文件名呢?