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ImageWithThumbsField

Author:
zenx
Posted:
December 23, 2008
Language:
Python
Version:
1.0
Tags:
image models fields thumbnail field thumbnails thumbs
Score:
3 (after 3 ratings)

Easy way to generate image thumbnails for your models. Works with any Storage Backend.

From: http://code.google.com/p/django-thumbs/

Usage example:

photo = ImageWithThumbsField(upload_to='images', sizes=((125,125),(300,200),)

To retrieve image URL, exactly the same way as with ImageField: my_object.photo.url

To retrieve thumbnails URL's just add the size to it: my_object.photo.url_125x125 my_object.photo.url_300x200

Note: The 'sizes' attribute is not required. If you don't provide it, ImageWithThumbsField will act as a normal ImageField

How it works:

For each size in the 'sizes' atribute of the field it generates a thumbnail with that size and stores it following this format:

available_filename.[width]x[height].extension

Where 'available_filename' is the available filename returned by the storage backend for saving the original file.

Following the usage example above: For storing a file called "photo.jpg" it saves: photo.jpg (original file) photo.125x125.jpg (first thumbnail) photo.300x200.jpg (second thumbnail)

With the default storage backend if photo.jpg already exists it will use these filenames: photo_.jpg photo_.125x125.jpg photo_.300x200.jpg

Note: It assumes that if filename "any_filename.jpg" is available filenames with this format "any_filename.[widht]x[height].jpg" will be available, too.

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# -*- encoding: utf-8 -*-
"""
django-thumbs by Antonio Melé
http://code.google.com/p/django-thumbs/
http://django.es
"""
from django.db.models import ImageField
from django.db.models.fields.files import ImageFieldFile
from PIL import Image
from django.core.files.base import ContentFile
import cStringIO

def generate_thumb(img, thumb_size, format):
    """
    Generates a thumbnail image and returns a ContentFile object with the thumbnail
    
    Parameters:
    ===========
    img         File object
    
    thumb_size  desired thumbnail size, ie: (200,120)
    
    format      format of the original image ('jpeg','gif','png',...)
                (this format will be used for the generated thumbnail, too)
    """
    
    img.seek(0) # see http://code.djangoproject.com/ticket/8222 for details
    image = Image.open(img)
    
    # Convert to RGB if necessary
    if image.mode not in ('L', 'RGB'):
        image = image.convert('RGB')
        
    # get size
    thumb_w, thumb_h = thumb_size
    # If you want to generate a square thumbnail
    if thumb_w == thumb_h:
        # quad
        xsize, ysize = image.size
        # get minimum size
        minsize = min(xsize,ysize)
        # largest square possible in the image
        xnewsize = (xsize-minsize)/2
        ynewsize = (ysize-minsize)/2
        # crop it
        image2 = image.crop((xnewsize, ynewsize, xsize-xnewsize, ysize-ynewsize))
        # load is necessary after crop                
        image2.load()
        # thumbnail of the cropped image (with ANTIALIAS to make it look better)
        image2.thumbnail(thumb_size, Image.ANTIALIAS)
    else:
        # not quad
        image2 = image
        image2.thumbnail(thumb_size, Image.ANTIALIAS)
    
    io = cStringIO.StringIO()
    # PNG and GIF are the same, JPG is JPEG
    if format.upper()=='JPG':
        format = 'JPEG'
    
    image2.save(io, format)
    return ContentFile(io.getvalue())    

class ImageWithThumbsFieldFile(ImageFieldFile):
    """
    See ImageWithThumbsField for usage example
    """
    def __init__(self, *args, **kwargs):
        super(ImageWithThumbsFieldFile, self).__init__(*args, **kwargs)
        self.sizes = self.field.sizes
        
        if self.sizes:
            def get_size(self, size):
                if not self:
                    return ''
                else:
                    split = self.url.rsplit('.',1)
                    thumb_url = '%s.%sx%s.%s' % (split[0],w,h,split[1])
                    return thumb_url
                    
            for size in self.sizes:
                (w,h) = size
                setattr(self, 'url_%sx%s' % (w,h), get_size(self, size))
                
    def save(self, name, content, save=True):
        super(ImageWithThumbsFieldFile, self).save(name, content, save)
        
        if self.sizes:
            for size in self.sizes:
                (w,h) = size
                split = self._name.rsplit('.',1)
                thumb_name = '%s.%sx%s.%s' % (split[0],w,h,split[1])
                
                # you can use another thumbnailing function if you like
                thumb_content = generate_thumb(content, size, split[1])
                
                thumb_name_ = self.storage.save(thumb_name, thumb_content)        
                
                if not thumb_name == thumb_name_:
                    raise ValueError('There is already a file named %s' % thumb_name)
        
    def delete(self, save=True):
        name=self.name
        super(ImageWithThumbsFieldFile, self).delete(save)
        if self.sizes:
            for size in self.sizes:
                (w,h) = size
                split = name.rsplit('.',1)
                thumb_name = '%s.%sx%s.%s' % (split[0],w,h,split[1])
                try:
                    self.storage.delete(thumb_name)
                except:
                    pass
                        
class ImageWithThumbsField(ImageField):
    attr_class = ImageWithThumbsFieldFile
    """
    Usage example:
    ==============
    photo = ImageWithThumbsField(upload_to='images', sizes=((125,125),(300,200),)
    
    To retrieve image URL, exactly the same way as with ImageField:
        my_object.photo.url
    To retrieve thumbnails URL's just add the size to it:
        my_object.photo.url_125x125
        my_object.photo.url_300x200
    
    Note: The 'sizes' attribute is not required. If you don't provide it, 
    ImageWithThumbsField will act as a normal ImageField
        
    How it works:
    =============
    For each size in the 'sizes' atribute of the field it generates a 
    thumbnail with that size and stores it following this format:
    
    available_filename.[width]x[height].extension

    Where 'available_filename' is the available filename returned by the storage
    backend for saving the original file.
    
    Following the usage example above: For storing a file called "photo.jpg" it saves:
    photo.jpg          (original file)
    photo.125x125.jpg  (first thumbnail)
    photo.300x200.jpg  (second thumbnail)
    
    With the default storage backend if photo.jpg already exists it will use these filenames:
    photo_.jpg
    photo_.125x125.jpg
    photo_.300x200.jpg
    
    Note: django-thumbs assumes that if filename "any_filename.jpg" is available 
    filenames with this format "any_filename.[widht]x[height].jpg" will be available, too.
    
    To do:
    ======
    Add method to regenerate thubmnails
    
    """
    def __init__(self, verbose_name=None, name=None, width_field=None, height_field=None, sizes=None, **kwargs):
        self.verbose_name=verbose_name
        self.name=name
        self.width_field=width_field
        self.height_field=height_field
        self.sizes = sizes
        super(ImageField, self).__init__(**kwargs)

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Comments

olau (on January 20, 2009):

Interesting! However, based on my experience you need to check the file extension or it might break the site if somebody uploads a .png without a .png extension (like "MYPHOTO12" instead of "MYPHOTO12.png"). Also you don't seem to handle the case of the original being smaller than the thumbnail (I believe this isn't handled correctly by PIL)

Another thing is that it's going be difficult to use this if there isn't a simple migration path whenever you need a new size. Something like starting up the shell and have it generate the missing images (it's probably pretty easy, just test for existence).

#

zenx (on January 22, 2009):

Thank you olau,

I will try to solve that issues in the next version :)

#

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