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Downloading Item Images

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.. currentmodule:: scrapy.contrib.pipeline.images

Scrapy provides an :doc:`item pipeline </topics/item-pipeline>` for downloading images attached to a particular item. For example, when you scrape products and also want to download their images locally.

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This pipeline, called the Images Pipeline and implemented in the :class:`ImagesPipeline` class, provides a convenient way for downloading and storing images locally with some additional features:

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Convert all downloaded images to a common format (JPG) and mode (RGB)
Avoid re-downloading images which were downloaded recently
Thumbnail generation
Check images width/height to make sure they meet a minimum constraint

This pipeline also keeps an internal queue of those images which are currently being scheduled for download, and connects those items that arrive containing the same image, to that queue. This avoids downloading the same image more than once when it's shared by several items.

The Python Imaging Library is used for thumbnailing and normalizing images to JPEG/RGB format, so you need to install that library in order to use the images pipeline.

Using the Images Pipeline

The typical workflow, when using the :class:`ImagesPipeline` goes like this:

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In a Spider, you scrape an item and put the URLs of its images into a pre-defined field, for example image_urls.
The item is returned from the spider and goes to the item pipeline.
When the item reaches the :class:`ImagesPipeline`, the URLs in the image_urls attribute are scheduled for download using the standard Scrapy scheduler and downloader (which means the scheduler and downloader middlewares are reused), but higher priority to process them before other pages to scrape. The item remains "locked" at that particular pipeline stage until the images have finish downloading (or fail for some reason).

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When the images finish downloading (or fail for some reason) the images gets another field populated with the path of the images downloaded, for example, image_paths. This attribute is a list of dictionaries containing information about the image downloaded, such as the downloaded path, and the original scraped url. This images in the list of the image_paths field would retain the same order of the original image_urls field, which is useful if you decide to use the first image in the list as the primary image.

Adjusting settings

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.. setting:: IMAGES_STORE

The first thing we need to do is tell the pipeline where to store the downloaded images, through the :setting:`IMAGES_STORE` setting:

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IMAGES_STORE = '/path/to/valid/dir'

Implementing the ImagePipeline

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.. module:: scrapy.contrib.pipeline.images
   :synopsis: Images Pipeline

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.. method:: get_media_requests(item, info)

   As seen on the workflow, the pipeline will get the URLs of the images to
   download from the item. In order to do this, you must override the
   :meth:`~MyImagesPipeline.get_media_requests` method and return a Request for each
   image URL::

      def get_media_requests(self, item, info):
          for image_url in item['image_urls']:
              yield Request(image_url)

   Those requests will be processed by the pipeline and, when they have finished
   downloading, the results will be sent to the
   :meth:`~MyImagesPipeline.item_completed` method, as a list of 2-element tuples.
   Each tuple will contain ``(success, image_info_or_failure)`` where:

   * ``success`` is a boolean which is ``True`` if the image was downloading
     successfully or ``False`` if it failed for some reason

   * ``image_info_or_error`` is a dict containing the following keys (if success
     is ``True``) or a `Twisted Failure`_ if there was a problem.

     * ``url`` - the url where the image was downloaded from. This is the url of
       the request returned from the :meth:`~MyImagesPipeline.get_media_requests`
       method.

     * ``path`` - the path (relative to :setting:`IMAGES_STORE`) where the image
       was stored

     * ``checksum`` - a `MD5`_ hash of the image contents

   .. _Twisted Failure: http://twistedmatrix.com/documents/8.2.0/api/twisted.python.failure.Failure.html
   .. _MD5: http://en.wikipedia.org/wiki/MD5

   The list of tuples received by :meth:`~MyImagesPipeline.item_completed` is
   guaranteed to retain the same order of the requests returned from the
   :meth:`~MyImagesPipeline.get_media_requests` method.

   Here's a typical an example value of ``results`` argumentt::

       [(True,
         {'checksum': '2b00042f7481c7b056c4b410d28f33cf',
          'path': '7d97e98f8af710c7e7fe703abc8f639e0ee507c4.jpg',
          'url': 'http://www.example.com/images/product1.jpg'}),
        (True,
         {'checksum': 'b9628c4ab9b595f72f280b90c4fd093d',
          'path': '1ca5879492b8fd606df1964ea3c1e2f4520f076f',
          'url': 'http://www.example.com/images/product2.jpg'}),
        (False,
         Failure(...))]

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.. method:: item_completed(results, items, info)

   The :meth:`~MyImagesPipeline.item_completed` method must return the output that
   will be sent to further item pipeline stages, so you must return (or drop) the
   item, as you would in any pipeline.

   Here is an example of :meth:`~MyImagesPipeline.item_completed` method where we
   store the downloaded image paths (passed in results) in the ``image_paths``
   item field, and we drop the item if it doesn't contain any images::

       from scrapy.core.exceptions import DropItem

       def item_completed(self, results, item, info):
           image_paths = [info['path'] for success, info in results if success]
           if not image_paths:
               raise DropItem("Item contains no images")
           item['image_paths'] = image_paths
           return item

So, the complete example of our pipeline would look like this:

from scrapy.contrib.pipeline.images import ImagesPipeline
from scrapy.core.exceptions import DropItem

class MyImagesPipeline(ImagesPipeline):

    def get_media_requests(self, item, info):
        for image_url in item['image_urls']:
            yield Request(image_url)

    def item_completed(self, results, item, info):
        image_paths = [info['path'] for success, info in results if success]
        if not image_paths:
            raise DropItem("Item contains no images")
        item['image_paths'] = image_paths
        return item

Image expiration

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Unknown directive type "setting".

.. setting:: IMAGES_EXPIRES

The Image Pipeline avoids downloading images that were downloaded recently. To adjust this retention delay use the :setting:`IMAGES_EXPIRES` setting, which specifies the delay in number of days:

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# 90 days of delay for image expiration
IMAGES_EXPIRES = 90

Thumbnail generation

The Images Pipeline can automatically create thumbnails of the downloaded images.

In order use this feature you must set the :attr:`~ImagesPipeline.THUMBS` to a tuple of (size_name, (width, height)) tuples.

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Here are some examples examples.

Using numeric names:

THUMBS = (
    ('50', (50, 50)),
    ('110', (110, 110)),
)

Using textual names:

THUMBS = (
    ('small', (50, 50)),
    ('big', (270, 270)),
)

When you use this feature, the Images Pipeline will create thumbnails of the each specified size with this format:

IMAGES_STORE/thumbs/<image_id>/<size_name>.jpg

Where:

<image_id> is the SHA1 hash of the image url
<size_name> is the one specified in the THUMBS attribute

Example with using 50 and 110 thumbnail names:

IMAGES_STORE/thumbs/63bbfea82b8880ed33cdb762aa11fab722a90a24/50.jpg
IMAGES_STORE/thumbs/63bbfea82b8880ed33cdb762aa11fab722a90a24/110.jpg

Example with using small and big thumbnail names:

IMAGES_STORE/thumbs/63bbfea82b8880ed33cdb762aa11fab722a90a24/small.jpg
IMAGES_STORE/thumbs/63bbfea82b8880ed33cdb762aa11fab722a90a24/big.jpg

Checking image size

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.. setting:: IMAGES_MIN_HEIGHT

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.. setting:: IMAGES_MIN_WIDTH

You can drop images which are too small, by specifying the minimum allowed size in the :setting:`IMAGES_MIN_HEIGHT` and :setting:`IMAGES_MIN_WIDTH` settings.

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For example:

IMAGES_MIN_HEIGHT = 110
IMAGES_MIN_WIDTH = 110

API Reference

ImagesPipeline

A pipeline to download images attached to items, for example product images.

To enable this pipeline you must set :setting:`IMAGES_STORE` to a valid directory that will be used for storing the downloaded images. Otherwise the pipeline will remain disabled, even if you include it in the :setting:`ITEM_PIPELINES` setting.

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.. method:: get_media_requests(item, info)

   Return a list of Request objects to download images for this item.

   Must return ``None`` or an iterable.

   By default it returns ``None`` which means there are no images to
   download for the item.

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.. method:: item_completed(results, item, info)

   Method called when all image requests for a single item have been
   downloaded (or failed).

   The output of this method is used as the output of the Image Pipeline
   stage.

   This method must returns the item itself or raise a
   :exc:`~scrapy.core.exceptions.DropItem` exception.

   By default, it returns the item.

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Unknown directive type "attribute".

.. attribute:: THUMBS

   List of thumbnails to generate for the images. See
   :ref:`topics-images-thumbnails`.

</html>

9.9 KiB Raw Blame History

Downloading Item Images

Using the Images Pipeline

Adjusting settings

Implementing the ImagePipeline

Image expiration

Thumbnail generation

Checking image size

API Reference

ImagesPipeline

9.9 KiB

Raw Blame History