undermythumb is a simple thumbnailing library for Django with a twist: its fields can optionally fall back to thumbnails from another field.
This app is currently used around Pitchfork, and is under active development.
Issues can be reported here.
At Pitchfork, we needed a simple way to cut thumbnails, place them on the field’s storage, do without fancy renderers we’d never use, and give editors a simple way to override auto-generated thumbnails without littering our templates with unnecessary logic.
In models.py:
from django.db import models
from undermythumb.fields import (ImageWithThumbnailsField,
ImageFallbackField)
from undermythumb.renderers import CropRenderer
class BlogPost(models.Model):
title = models.CharField(max_length=100)
# an image with thumbnails
artwork = ImageWithThumbnailsField(
max_length=255,
upload_to='artwork/',
thumbnails=(('homepage_image', CropRenderer(300, 150)),
('pagination_image', CropRenderer(150, 75))),
help_text='Blog post header artwork.')
# an override field, capable of rolling up a dotted path
# if the field is empty.
# ``fallback_path`` should point to something that returns an ``ImageFieldFile``,
# or anything that has an ``url`` attribute, and displays an image.
#
# under the hood, this is just an ImageField.
homepage_image = ImageFallbackField(
fallback_path='artwork.thumbnails.homepage_image',
upload_to='artwork/',
help_text='Optional override for "homepage_image" thumbnail.')
def __unicode__(self):
return self.title
In a template, where object is an instance of BlogPost:
<!-- does the job: auto-generated thumbnail from "artwork" -->
<img src="{{ object.artwork.thumbnails.homepage_image.url }}" />
<!-- smarter: value of "homepage_image", or, if empty, value of "artwork.thumbnails.homepage_image" -->
<img src="{{ object.homepage_image.url }}" />
Sometimes system generated thumbnails are ugly, or need to be overridden. In this case, offering an override field allows designers and editors a way to control the thumbnail used across your site.
Sometimes, default thumbnails are perfect, and no additional work is required.
The easiest way to account for both scenarios is to have a single field that allows an optional override, and can fall back to another image if no override is needed.
This way,