Django view that converts a RasterField to PNG

geodjango-postgis-raster-to-png.py

from django.http import HttpResponse
from django.db.models import BinaryField, Func, F, Value, CharField

from .models import MyModel


def view_png(request):
    """Return a PostGIS raster as a PNG image."""
    # MyModel is a django model with a RasterField named "rast".
    # Note: ST_AsGdalRaster can reproject the data,
    # see http://postgis.net/docs/manual-dev/RT_ST_AsGDALRaster.html
    o = MyModel.objects.all().annotate(
        img=Func(
            F('rast'), 
            Value('PNG', output_field=CharField()),
            output_field=BinaryField(),
            function='st_asgdalraster'
        )
    ).first()
    response = HttpResponse(content_type="image/png")
    response.write(o.image.tobytes())
    return response