panikweb/paniktags/templatetags/thumbnails.py

   1 # initiated from http://djangosnippets.org/snippets/2145/
   2
   3 import os
   4 import re
   5 from PIL import Image
   6
   7 from django.conf import settings
   8
   9 from django.db.models.signals import post_save, pre_delete
  10 from django.template import Library
  11
  12 register = Library()
  13
  14 def thumbnail(image, size='100x100'):
  15     # defining the size
  16     x, y = [int(x) for x in size.split('x')]
  17     # defining the filename and the miniature filename
  18     try:
  19         filehead, filetail = os.path.split(image.path)
  20     except (AttributeError, ValueError):
  21         # return transparent pixel if the image doesn't actually exist
  22         return 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAAACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5CYII='
  23     basename, format = os.path.splitext(filetail)
  24     if format.lower() not in ('.jpg', '.jpeg'):
  25         format = '.png'
  26     miniature = basename + '__' + size + format
  27     filename = image.path
  28     miniature_filename = os.path.join(filehead, miniature)
  29     filehead, filetail = os.path.split(image.url)
  30     miniature_url = filehead + '/' + miniature
  31     if os.path.exists(miniature_filename) and \
  32             os.path.getmtime(filename) > os.path.getmtime(miniature_filename):
  33         os.unlink(miniature_filename)
  34     # if the image wasn't already resized, resize it
  35     if not os.path.exists(miniature_filename) and os.path.exists(filename):
  36         image = Image.open(filename)
  37         if abs( (1.0*x/y) - (1.0*image.size[0]/image.size[1]) ) > 0.1:
  38             # aspect ratio change, crop the image first
  39             box = [0, 0, image.size[0], int(image.size[0] * (1.0*y/x))]
  40
  41             if box[2] > image.size[0]:
  42                 box = [int(t*(1.0*image.size[0]/box[2])) for t in box]
  43             if box[3] > image.size[1]:
  44                 box = [int(t*(1.0*image.size[1]/box[3])) for t in box]
  45
  46             if image.size[0] > image.size[1]: # landscape
  47                 box[0] = (image.size[0] - box[2]) / 2 # keep the middle
  48                 box[2] += box[0]
  49             else:
  50                 box[1] = (image.size[1] - box[3]) / 4 # keep mostly the top
  51                 box[3] += box[1]
  52
  53             image = image.crop(box)
  54         image = image.resize([x, y], Image.ANTIALIAS)
  55         try:
  56             image.save(miniature_filename, image.format, quality=90, optimize=1)
  57         except:
  58             image.save(miniature_filename, image.format, quality=90)
  59
  60     return miniature_url
  61
  62
  63 register.filter(thumbnail)
  64
  65
  66 def clean_thumb(sender, instance, **kwargs):
  67     if not hasattr(instance, 'image'):
  68         return
  69     if not instance.image:
  70         return
  71     name, ext = os.path.splitext(os.path.basename(instance.image.name))
  72     exp = '^%s__\d+x\d+x[0-1]{1}\%s' % (name, ext)
  73     for file_path in os.listdir(settings.MEDIA_ROOT):
  74         if re.search(exp, file_path):
  75             os.unlink(settings.MEDIA_ROOT + file_path)
  76
  77
  78 post_save.connect(clean_thumb)
  79 pre_delete.connect(clean_thumb)