From 828e3b1335e2614d338a630fd5b5f88d38a6b5d2 Mon Sep 17 00:00:00 2001 From: Ivor Bosloper Date: Wed, 4 Mar 2020 13:45:15 +0100 Subject: [PATCH] Refs #30489 -- Made from_pgraster()/to_pgraster() use BANDTYPE_FLAG_HASNODATA and bitwise operators for nodata flag. --- .../contrib/gis/db/backends/postgis/const.py | 3 +++ .../gis/db/backends/postgis/pgraster.py | 21 ++++++++++--------- 2 files changed, 14 insertions(+), 10 deletions(-) diff --git a/django/contrib/gis/db/backends/postgis/const.py b/django/contrib/gis/db/backends/postgis/const.py index 4b511eb149..6091acc7b4 100644 --- a/django/contrib/gis/db/backends/postgis/const.py +++ b/django/contrib/gis/db/backends/postgis/const.py @@ -41,3 +41,6 @@ STRUCT_SIZE = { 'f': 4, # Float 'd': 8, # Double } + +# See https://trac.osgeo.org/postgis/wiki/WKTRaster/RFC/RFC1_V0SerialFormat#Pixeltypeandstorageflag +BANDTYPE_FLAG_HASNODATA = 1 << 6 diff --git a/django/contrib/gis/db/backends/postgis/pgraster.py b/django/contrib/gis/db/backends/postgis/pgraster.py index e6c1b2247c..1a4dc9aa23 100644 --- a/django/contrib/gis/db/backends/postgis/pgraster.py +++ b/django/contrib/gis/db/backends/postgis/pgraster.py @@ -3,8 +3,8 @@ import struct from django.forms import ValidationError from .const import ( - GDAL_TO_POSTGIS, GDAL_TO_STRUCT, POSTGIS_HEADER_STRUCTURE, POSTGIS_TO_GDAL, - STRUCT_SIZE, + BANDTYPE_FLAG_HASNODATA, GDAL_TO_POSTGIS, GDAL_TO_STRUCT, + POSTGIS_HEADER_STRUCTURE, POSTGIS_TO_GDAL, STRUCT_SIZE, ) @@ -48,10 +48,10 @@ def from_pgraster(data): pixeltype, data = chunk(data, 2) pixeltype = unpack('B', pixeltype)[0] - # Subtract nodata byte from band nodata value if it exists - has_nodata = pixeltype >= 64 + # Remove nodata byte from band nodata value if it exists. + has_nodata = pixeltype & BANDTYPE_FLAG_HASNODATA if has_nodata: - pixeltype -= 64 + pixeltype &= ~BANDTYPE_FLAG_HASNODATA # Convert datatype from PostGIS to GDAL & get pack type and size pixeltype = POSTGIS_TO_GDAL[pixeltype] @@ -116,12 +116,13 @@ def to_pgraster(rast): # and the nodata value. # # The 8BUI stores both the PostGIS pixel data type and a nodata flag. - # It is composed as the datatype integer plus 64 as a flag for existing - # nodata values: - # 8BUI_VALUE = PG_PIXEL_TYPE (0-11) + FLAG (0 or 64) + # It is composed as the datatype with BANDTYPE_FLAG_HASNODATA (1 << 6) + # for existing nodata values: + # 8BUI_VALUE = PG_PIXEL_TYPE (0-11) | BANDTYPE_FLAG_HASNODATA # # For example, if the byte value is 71, then the datatype is - # 71-64 = 7 (32BSI) and the nodata value is True. + # 71 & ~BANDTYPE_FLAG_HASNODATA = 7 (32BSI) + # and the nodata value is True. structure = 'B' + GDAL_TO_STRUCT[band.datatype()] # Get band pixel type in PostGIS notation @@ -129,7 +130,7 @@ def to_pgraster(rast): # Set the nodata flag if band.nodata_value is not None: - pixeltype += 64 + pixeltype |= BANDTYPE_FLAG_HASNODATA # Pack band header bandheader = pack(structure, (pixeltype, band.nodata_value or 0))