django-large-image

Image tile serving in Django made easy

django-large-image is an abstraction of large-image for use with django-rest-framework providing view mixins for endpoints to work with large images in Django -- specifically geared towards geospatial and medical image tile serving.

Created by Kitware, Inc.

OpenAPI Documentation	Tiles Endpoint

Overview

This package ports Kitware's large-image to Django by providing a set of abstract, mixin API view classes that will handle tile serving, fetching metadata from images, and extracting regions of interest.

django-large-image is an optionally installable Django app with a few classes that can be mixed into a Django project (or application)'s drf-based views to provide tile serving endpoints out of the box. Notably, django-large-image is designed to work specifically with FileFeild interfaces with development being tailored to Kitware's S3FileField. We are working to also support GeoDjango's GDALRaster in the future

This package ships with pre-made HTML templates for rendering geospatial image tiles with CesiumJS and non-geospatial image tiles with GeoJS.

Features

Rich set of RESTful endpoints to extract information from large image formats:

• Image metadata (/metadata, /internal_metadata)
• Tile serving (/tiles/{z}/{x}/{y}.png?projection=EPSG:3857)
• Region extraction (/region.tif?left=v&right=v&top=v&bottom=v)
• Image thumbnails (/thumbnail)
• Individual pixels (/pixel?left=v&top=v)
• Band histograms (/histogram)

Support for general FileFeild's or File URLs

• Supports django's FileFeild
• Supports S3FileField
• Supports GDAL's Virtual File System for s3://, ftp://, etc. URLs

Miscellaneous:

• Admin interface widget for viewing image tiles.
• Caching - tile sources are cached for rapid file re-opening
  • tiles and thumbnails are cached to prevent recreating these data on multiple requests
• Easily extensible SSR templates for tile viewing with CesiumJS and GeoJS
• OpenAPI specification

Installation

Out of the box, django-large-image only depends of the core large-image module, but you will need a large-image-source-* module in order for this to work. Most of our users probably want to work with geospatial images so we will focus on the large-image-source-gdal case, but it is worth noting that large-image has source modules for a wide variety of image formats (e.g., medical image formats for microscopy).

See large-image's installation instructions for more details.

Tip: installing GDAL is notoriously difficult, so at Kitware we provide pre-built Python wheels with the GDAL binary bundled for easily installation in production environments. To install our GDAL wheel, use: pip install --find-links https://girder.github.io/large_image_wheels GDAL

pip install \
  --find-links https://girder.github.io/large_image_wheels \
  django-large-image \
  large-image-source-gdal

Usage

Simply install the app and mixin the LargeImageViewMixin class to your existing django-rest-framework viewsets and specify the FILE_FIELD_NAME as the string name of the FileField in which your image data are saved.

# settings.py
INSTALLED_APPS = [
    ...,
    'django_large_image',
]

# viewsets.py
from django_large_image.rest import LargeImageViewMixin

class MyModelViewset(viewsets.GenericViewSet, LargeImageViewMixin):
  ...  # configuration for your model's viewset
  FILE_FIELD_NAME = 'field_name'

And that's it!

Example Code

To use the mixin classes provided here, create a model, serializer, and view in your Django project like so:

# models.py
from django.db import models
from rest_framework import serializers


class ImageFile(models.Model):
    name = models.TextField()
    file = models.FileField()


class ImageFileSerializer(serializers.ModelSerializer):
    class Meta:
        model = ImageFile
        fields = '__all__'

# admin.py
from django.contrib import admin
from example.core.models import ImageFile


@admin.register(ImageFile)
class ImageFileAdmin(admin.ModelAdmin):
    list_display = ('pk', 'name')

Then create the viewset, mixing in the django-large-image view class:

# viewsets.py
from example.core import models
from rest_framework import mixins, viewsets

from django_large_image.rest import LargeImageViewMixin


class ImageFileDetailView(
    mixins.ListModelMixin,
    viewsets.GenericViewSet,
    LargeImageViewMixin,
):
    queryset = models.ImageFile.objects.all()
    serializer_class = models.ImageFileSerializer

    # for `django-large-image`: the name of the image FileField on your model
    FILE_FIELD_NAME = 'file'

Then register the URLs:

# urls.py
from django.urls import path
from example.core.viewsets import ImageFileDetailView
from rest_framework.routers import SimpleRouter

router = SimpleRouter(trailing_slash=False)
router.register(r'api/image-file', ImageFileDetailView, basename='image-file')

urlpatterns = [
  path('', include('django_large_image.urls')),  # Additional diagnostic URLs from django-large-image
] + router.urls

You can also use an admin widget for your model:

<!-- templates/admin/myapp/imagefile/change_form.html -->
{% extends "admin/change_form.html" %}

{% block after_field_sets %}

<script>
  var baseEndpoint = 'api/image-file';
</script>

{% include 'admin/django_large_image/_include/geojs.html' %}

{% endblock %}

Please note the example Django project in the project/ directory of this repository that shows how to use django-large-image in a girder-4 project.

Customization

The LargeImageViewMixin is modularly designed and able to be subclassed for your project's needs. While the provided LargeImageViewMixin handles FileFeild-interfaces, you can easily extend it to handle any mechanism of data storage.

In the following example, I will show how to use GDAL compatible VSI paths from a model that stores s3:// or https:// URLs.

# model.py
from django.db import models
from rest_framework import serializers


class URLImageFile(models.Model):
    name = models.TextField()
    url = models.TextField()


class URLImageFileSerializer(serializers.ModelSerializer):
    class Meta:
        model = URLImageFile
        fields = '__all__'

# viewsets.py
from example.core import models
from rest_framework import mixins, viewsets

from django_large_image.rest import LargeImageViewMixin
from django_large_image.utilities import make_vsi


class URLLargeImageViewMixin(LargeImageViewMixin):
    def get_path(self, request, pk):
        object = self.get_object()
        return make_vsi(object.url)


class URLImageFileDetailView(
    mixins.ListModelMixin,
    viewsets.GenericViewSet,
    URLLargeImageViewMixin,
):
    queryset = models.URLImageFile.objects.all()
    serializer_class = models.URLImageFileSerializer

Here is a good test image: https://oin-hotosm.s3.amazonaws.com/59c66c5223c8440011d7b1e4/0/7ad397c0-bba2-4f98-a08a-931ec3a6e943.tif