ImageKit is a Django app that helps you to add variations of uploaded images to your models. These variations are called "specs" and can include things like different sizes (e.g. thumbnails) and black and white versions.

1. pip install django-imagekit (or clone the source and put the imagekit module on your path)
2. Add 'imagekit' to your INSTALLED_APPS list in your project's settings.py

Much like django.db.models.ImageField, Specs are defined as properties of a model class:

from django.db import models
from imagekit.models import ImageSpec

class Photo(models.Model):
    original_image = models.ImageField(upload_to='photos')
    formatted_image = ImageSpec(image_field='original_image', format='JPEG',
            options={'quality': 90})

Accessing the spec through a model instance will create the image and return an ImageFile-like object (just like with a normal django.db.models.ImageField):

photo = Photo.objects.all()[0]
photo.original_image.url # > '/media/photos/birthday.tiff'
photo.formatted_image.url # > '/media/cache/photos/birthday_formatted_image.jpeg'

Check out imagekit.models.ImageSpec for more information.

The real power of ImageKit comes from processors. Processors take an image, do something to it, and return the result. By providing a list of processors to your spec, you can expose different versions of the original image:

from django.db import models
from imagekit.models import ImageSpec
from imagekit.processors import resize, Adjust

class Photo(models.Model):
    original_image = models.ImageField(upload_to='photos')
    thumbnail = ImageSpec([Adjust(contrast=1.2, sharpness=1.1),
            resize.Crop(50, 50)], image_field='original_image',
            format='JPEG', options={'quality': 90})

The thumbnail property will now return a cropped image:

photo = Photo.objects.all()[0]
photo.thumbnail.url # > '/media/cache/photos/birthday_thumbnail.jpeg'
photo.thumbnail.width # > 50
photo.original_image.width # > 1000

The original image is not modified; thumbnail is a new file that is the result of running the imagekit.processors.resize.Crop processor on the original.

The imagekit.processors module contains processors for many common image manipulations, like resizing, rotating, and color adjustments. However, if they aren't up to the task, you can create your own. All you have to do is implement a process() method:

class Watermark(object):
    def process(self, image):
        # Code for adding the watermark goes here.
        return image

class Photo(models.Model):
    original_image = models.ImageField(upload_to='photos')
    watermarked_image = ImageSpec([Watermark()], image_field='original_image',
            format='JPEG', options={'quality': 90})

ImageKit also contains a class named imagekit.admin.AdminThumbnail for displaying specs (or even regular ImageFields) in the Django admin change list. AdminThumbnail is used as a property on Django admin classes:

from django.contrib import admin
from imagekit.admin import AdminThumbnail
from .models import Photo


class PhotoAdmin(admin.ModelAdmin):
    list_display = ('__str__', 'admin_thumbnail')
    admin_thumbnail = AdminThumbnail(image_field='thumbnail')


admin.site.register(Photo, PhotoAdmin)

AdminThumbnail can even use a custom template. For more information, see imagekit.admin.AdminThumbnail.