Django Image field with thumbnail.

ImageWithThumbField.py

from django.db.models import ImageField
from django.db.models import signals
from django.db.models.fields.files import ImageFieldFile

from PIL import Image
import os


def name_thumb(str):
    """ Function for generating thumbnail name from original file. """
    parts = str.split(u'.')
    parts[-2]+=u'_thumb'
    return u'.'.join(parts)


class ImageWithThumbFieldFile(ImageFieldFile):
    """ Extension to file field. """
    def get_thumb_url(self):
        try: # hack to check if file was passed
            self.file
        except:
            return
        return name_thumb(u"%s"%self)
    thumb_url = property(get_thumb_url)
    

class ImageWithThumbField(ImageField): 
    """ Model field for keeping a thumbnail next to actual image """
    attr_class = ImageWithThumbFieldFile   
    
    def db_type(self, connection):
        return 'Varchar(255)'    

    def __init__(self, verbose_name=None, name=None, twidth=120, theight=80, **kwargs):
        self.twidth, self.theight = twidth, theight
        super(ImageWithThumbField, self).__init__(verbose_name=verbose_name, name=name,**kwargs)
        
    def _save(self,**kwargs):
        image = getattr(kwargs['instance'], self.attname)

        try: # hack to check if file was passed
            image.file
        except:
            return

        thumb_path = name_thumb(image.path)
        
        if os.path.exists(thumb_path) and os.path.getmtime(image.path) > os.path.getmtime(thumb_path): #obsolete?
            os.unlink(thumb_path)

        if not os.path.exists(thumb_path):
            image = Image.open(image.path)
            image.thumbnail([self.twidth, self.theight], Image.ANTIALIAS)
            try:
                image.save(thumb_path, image.format, quality=90, optimize=1)
            except:
                image.save(thumb_path, image.format, quality=90)

    def _delete(self,**kwargs):
        image = getattr(kwargs['instance'], self.attname)

        try: # hack to check if file was passed
            image.file
        except:
            return

        if image.file:
            thumb_path = name_thumb(image.path)   
            try:
                os.unlink(image.path)
                os.unlink(thumb_path)
            except OSError:
                pass 
        
    def contribute_to_class(self, cls, name):
        super(ImageWithThumbField, self).contribute_to_class(cls, name)
        signals.post_save.connect(self._save, cls, True)
        signals.pre_delete.connect(self._delete, cls, True)  
        
    def get_internal_type(self):
        return 'ImageField'