boards/models/image.py

import hashlib
import os
from random import random
import time
from django.db import models
from boards import thumbs
from boards.models.base import Viewable

__author__ = 'neko259'


IMAGE_THUMB_SIZE = (200, 150)
IMAGES_DIRECTORY = 'images/'
FILE_EXTENSION_DELIMITER = '.'
HASH_LENGTH = 36

CSS_CLASS_IMAGE = 'image'
CSS_CLASS_THUMB = 'thumb'


class PostImageManager(models.Manager):
    def create_with_hash(self, image):
        image_hash = self.get_hash(image)
        existing = self.filter(hash=image_hash)
        if len(existing) > 0:
            post_image = existing[0]
        else:
            post_image = PostImage.objects.create(image=image)

        return post_image

    def get_hash(self, image):
        """
        Gets hash of an image.
        """
        md5 = hashlib.md5()
        for chunk in image.chunks():
            md5.update(chunk)
        return md5.hexdigest()


class PostImage(models.Model, Viewable):
    objects = PostImageManager()

    class Meta:
        app_label = 'boards'
        ordering = ('id',)

    def _update_image_filename(self, filename):
        """
        Gets unique image filename
        """

        path = IMAGES_DIRECTORY

        # TODO Use something other than random number in file name
        new_name = '{}{}.{}'.format(
            str(int(time.mktime(time.gmtime()))),
            str(int(random() * 1000)),
            filename.split(FILE_EXTENSION_DELIMITER)[-1:][0])

        return os.path.join(path, new_name)

    width = models.IntegerField(default=0)
    height = models.IntegerField(default=0)

    pre_width = models.IntegerField(default=0)
    pre_height = models.IntegerField(default=0)

    image = thumbs.ImageWithThumbsField(upload_to=_update_image_filename,
                                        blank=True, sizes=(IMAGE_THUMB_SIZE,),
                                        width_field='width',
                                        height_field='height',
                                        preview_width_field='pre_width',
                                        preview_height_field='pre_height')
    hash = models.CharField(max_length=HASH_LENGTH)

    def save(self, *args, **kwargs):
        """
        Saves the model and computes the image hash for deduplication purposes.
        """

        if not self.pk and self.image:
            self.hash = PostImage.objects.get_hash(self.image)
        super(PostImage, self).save(*args, **kwargs)

    def __str__(self):
        return self.image.url

    def get_view(self):
        return '<div class="{}">' \
               '<a class="{}" href="{full}">' \
               '<img class="post-image-preview"' \
               ' src="{}"' \
               ' alt="{}"' \
               ' width="{}"' \
               ' height="{}"' \
               ' data-width="{}"' \
               ' data-height="{}" />' \
               '</a>' \
               '</div>'\
            .format(CSS_CLASS_IMAGE, CSS_CLASS_THUMB,
                    self.image.url_200x150,
                    str(self.hash), str(self.pre_width),
                    str(self.pre_height), str(self.width), str(self.height), full=self.image.url)