title: Scrapy image download how to use custom filename
body: <p>For my <a href="http://doc.scrapy.org/index.html" rel="noreferrer">scrapy</a> project I'm currently using the <a href="http://doc.scrapy.org/topics/images.html#scrapy.contrib.pipeline.images.ImagesPipeline" rel="noreferrer">ImagesPipeline</a>. The downloaded images are <a href="http://doc.scrapy.org/topics/images.html#file-system-storage" rel="noreferrer">stored with a SHA1 hash</a> of their URLs as the file names.</p>
  
  <p><strong>How can I store the files using my own custom file names instead?</strong> </p>
  
  <p>What if my custom file name needs to contain another scraped field from the same item? e.g. use the <code>item['desc']</code> and the filename for the image with <code>item['image_url']</code>. If I understand correctly, that would involve somehow accessing the other item fields from the Image Pipeline. </p>
  
  <p>Any help will be appreciated.</p>