What I see is that when I load my page, it calls update_dimension_fields for every image. The model is simple.
class Photo(models.Model):
width = models.PositiveIntegerField(blank=True, null=True, editable=False, default="0")
height = models.PositiveIntegerField(blank=True, null=True, editable=False, default="0")
image = ImageField(upload_to=upload_to, width_field='width', height_field='height')
user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name="uploaded_photos")
title = models.CharField(max_length=255)
slug = extension_fields.AutoSlugField(populate_from='title', blank=True)
caption = models.CharField(max_length=255, blank=True)
date_added = models.DateTimeField(default=timezone.now)
class PhotoCollection(models.Model):
name = models.CharField('name', max_length=250)
slug = extension_fields.AutoSlugField(populate_from='name', blank=True)
description = models.TextField(blank=True)
user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name="uploaded_collections")
date_added = models.DateTimeField(default=timezone.now)
photos = models.ManyToManyField('photos.Photo', related_name='collections', blank=True)