如何在没有直接链接的情况下下载验证码图片

我试图从命令行客户端访问sci-hub.io，而不是打败它的验证码系统。当您将doi发布到其首页时，它将返回http://moscow.sci-hub.io/abc123blah/foo.pdf表单的pdf网址。如果您然后请求链接，您随机获得pdf或验证码。 CAPTCHA页面有这个来源：如何在没有直接链接的情况下下载验证码图片

<html> 
    <head> 
     <title>Для просмотра статьи разгадайте капчу</title> 
     <meta charset="UTF-8"> 
     <meta name="viewport" content="width=device-width, initial-scale=1.0"> 
    </head> 
    <body style = "background:white"> 
     <div> 
      <table style = "width:100%;height:100%"><tr><td style = "vertical-align:middle;text-align:center"> 
      <h2 style = "color:gray;font-family:sans-serif;padding:18px">для просмотра статьи разгадайте капчу</h2> 
      <p></p> 
      <form action = "" method = "POST"> 
       <p><img id="captcha" src="/captcha/securimage_show.php" /></p> 
       <input type="text" maxlength="6" name="captcha_code" style = "width:256px;font-size:18px;height:36px;margin-top:18px;text-align:center" autofocus /><br> 
       <a style = "color:gray;text-decoration:none" href="#" onclick="document.getElementById('captcha').src = '/captcha/securimage_show.php?' + Math.random(); return false">[ показать другую картинку ]</a> 
       <p style = "margin-top:22px"><input type = "submit" value= "Продолжить"></p> 
      </form> 
      </td></tr></table> 
     </div> 
    </body> 
</html>

所有我能想到做的是，要求securimage_show.php，保存图片，它显示给用户，抢它的解码，然后POST响应。一个例子PDF链接是http://moscow.sci-hub.io/291193c259b69cc057d74e3eb4965c4f/ong2014.pdf 喜欢的东西：

import requests 
from PIL import Image 
import io 

pdf_url = "http://moscow.sci-hub.io/3dcd1bf3b82ea549c0a72e9ab195ab78/walter2015.pdf" 

r1 = requests.get(pdf_url) 

if r1.headers['Content-Type'] != 'application/pdf': 
    print("Looks like Sci-hub gave us a captcha") 

    image = requests.get("http://moscow.sci-hub.io/captcha/securimage_show.php").content 
    img = io.BytesIO(image) 
    im = Image.open(img) 
    im.show() 
    captcha_text = input("Enter captcha text: ") 

    r2 = requests.post(pdf_url, data = {'captcha_code': captcha_text}) 

    if r2.headers['Content-Type'] != 'application/pdf': 
     print("Looks like Sci-hub gave us another captcha") 
    else: 
     with open("filename.pdf", 'wb') as f: 
      f.write(r.content) 
     print("saved!") 

else: 
    print("Got a PDF") 
    with open("filename.pdf", 'wb') as f: 
     f.write(r.content) 
    print("saved!")

我没有一种方法可以让我第一次请求PDF时生成的验证码原始图像。当我从securimage_show.php请求另一个验证码图像时，它会生成一个新的图像，以便POST响应不正确。我怎样才能解决这个问题？

来源

2017-04-09 pgcudahy

也许你应该在一个会话中执行两个操作？请参阅http://docs.python-requests.org/en/master/user/advanced/ –

感谢安德鲁指引我在正确的方向。我需要与请求建立会话。我假设这个会话来回传递一个cookie，以便服务器可以跟踪它发送给我的最新验证码。只是一个猜测，因为这对我来说仍然有点神奇。

import requests 
from PIL import Image 
from io import BytesIO 

pdf_url = "http://moscow.sci-hub.io/3dcd1bf3b82ea549c0a72e9ab195ab78/walter2015.pdf" 

s = requests.Session() 
r1 = s.get(pdf_url) 

if r1.headers['Content-Type'] != 'application/pdf': 
    print("Looks like Sci-hub gave us a captcha") 

    image = s.get("http://moscow.sci-hub.io/captcha/securimage_show.php").content 
    img = BytesIO(image) 
    im = Image.open(img) 
    im.show() 
    captcha_text = input("Enter captcha text: ") 

    r2 = s.post(pdf_url, data = {'captcha_code': captcha_text}) 

    if r2.headers['Content-Type'] != 'application/pdf': 
     print("Looks like Sci-hub gave us another captcha") 
    else: 
     with open("filename.pdf", 'wb') as f: 
      f.write(r2.content) 
     print("saved!") 

else: 
    print("Got a PDF") 
    with open("filename.pdf", 'wb') as f: 
     f.write(r1.content) 
    print("saved!")

来源

2017-04-10 14:42:47 pgcudahy

如何在没有直接链接的情况下下载验证码图片

回答

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