class Images(models.Model):
    image = models.ImageField()

    def save(self, *args, **kwargs):
        if self.image:
            img = Img.open(StringIO.StringIO(self.image.read()))
            if img.mode != 'RGB':
                img = img.convert('RGB')
            img.thumbnail((self.image.width/1.5,self.image.height/1.5), Img.ANTIALIAS)
            output = StringIO.StringIO()
            img.save(output, format='JPEG', quality=70)
            output.seek(0)
            self.image= InMemoryUploadedFile(output,'ImageField', "file.jpg", 'image/jpeg', output.len, None)
        super(Images, self).save(*args, **kwargs)