Fixed #30489 -- Fixed RasterField deserialization with pixeltype flags.

Thanks Ivor Bosloper for the original patch.

django/contrib/gis/db/backends/postgis/const.py

@@ -42,5 +42,11 @@ STRUCT_SIZE = {
     'd': 8,  # Double
 }
 
+# Pixel type specifies type of pixel values in a band. Storage flag specifies
+# whether the band data is stored as part of the datum or is to be found on the
+# server's filesystem. There are currently 11 supported pixel value types, so 4
+# bits are enough to account for all. Reserve the upper 4 bits for generic
+# flags.
 # See https://trac.osgeo.org/postgis/wiki/WKTRaster/RFC/RFC1_V0SerialFormat#Pixeltypeandstorageflag
+BANDTYPE_PIXTYPE_MASK = 0x0F
 BANDTYPE_FLAG_HASNODATA = 1 << 6

django/contrib/gis/db/backends/postgis/pgraster.py

@@ -3,8 +3,8 @@ import struct
 from django.forms import ValidationError
 
 from .const import (
-    BANDTYPE_FLAG_HASNODATA, GDAL_TO_POSTGIS, GDAL_TO_STRUCT,
-    POSTGIS_HEADER_STRUCTURE, POSTGIS_TO_GDAL, STRUCT_SIZE,
+    BANDTYPE_FLAG_HASNODATA, BANDTYPE_PIXTYPE_MASK, GDAL_TO_POSTGIS,
+    GDAL_TO_STRUCT, POSTGIS_HEADER_STRUCTURE, POSTGIS_TO_GDAL, STRUCT_SIZE,
 )
 
 
@@ -45,13 +45,9 @@ def from_pgraster(data):
     pixeltypes = []
     while data:
         # Get pixel type for this band
-        pixeltype, data = chunk(data, 2)
-        pixeltype = unpack('B', pixeltype)[0]
-
-        # Remove nodata byte from band nodata value if it exists.
-        has_nodata = pixeltype & BANDTYPE_FLAG_HASNODATA
-        if has_nodata:
-            pixeltype &= ~BANDTYPE_FLAG_HASNODATA
+        pixeltype_with_flags, data = chunk(data, 2)
+        pixeltype_with_flags = unpack('B', pixeltype_with_flags)[0]
+        pixeltype = pixeltype_with_flags & BANDTYPE_PIXTYPE_MASK
 
         # Convert datatype from PostGIS to GDAL & get pack type and size
         pixeltype = POSTGIS_TO_GDAL[pixeltype]
@@ -68,8 +64,8 @@ def from_pgraster(data):
         band, data = chunk(data, pack_size * header[10] * header[11])
         band_result = {'data': bytes.fromhex(band)}
 
-        # If the nodata flag is True, set the nodata value.
-        if has_nodata:
+        # Set the nodata value if the nodata flag is set.
+        if pixeltype_with_flags & BANDTYPE_FLAG_HASNODATA:
             band_result['nodata_value'] = nodata
 
         # Append band data to band list

tests/gis_tests/rasterapp/test_rasterfield.py

@@ -8,7 +8,7 @@ from django.contrib.gis.geos import GEOSGeometry
 from django.contrib.gis.measure import D
 from django.contrib.gis.shortcuts import numpy
 from django.db import connection
-from django.db.models import Q
+from django.db.models import F, Func, Q
 from django.test import TransactionTestCase, skipUnlessDBFeature
 from django.test.utils import CaptureQueriesContext
 
@@ -51,6 +51,26 @@ class RasterFieldTest(TransactionTestCase):
         qs = RasterModel.objects.all()
         qs[0].rast.bands[0].data()
 
+    def test_deserialize_with_pixeltype_flags(self):
+        no_data = 3
+        rast = GDALRaster({
+            'srid': 4326,
+            'origin': [0, 0],
+            'scale': [-1, 1],
+            'skew': [0, 0],
+            'width': 1,
+            'height': 1,
+            'nr_of_bands': 1,
+            'bands': [{'data': [no_data], 'nodata_value': no_data}],
+        })
+        r = RasterModel.objects.create(rast=rast)
+        RasterModel.objects.filter(pk=r.pk).update(
+            rast=Func(F('rast'), function='ST_SetBandIsNoData'),
+        )
+        r.refresh_from_db()
+        self.assertEquals(r.rast.bands[0].data(), [[no_data]])
+        self.assertEquals(r.rast.bands[0].nodata_value, no_data)
+
     def test_model_creation(self):
         """
         Test RasterField through a test model.