Fixed #28576 -- Added color interpretation method to GDALBand.

AUTHORS

@@ -591,6 +591,7 @@ answer newbie questions, and generally made Django that much better:
     Nebojša Dorđević
     Ned Batchelder <http://www.nedbatchelder.com/>
     Nena Kojadin <nena@kiberpipa.org>
+    Niall Dalton <niall.dalton12@gmail.com>
     Niall Kelly <duke.sam.vimes@gmail.com>
     Nick Efford <nick@efford.org>
     Nick Lane <nick.lane.au@gmail.com>

django/contrib/gis/gdal/prototypes/raster.py

@@ -75,6 +75,7 @@ get_band_index = int_output(std_call('GDALGetBandNumber'), [c_void_p])
 get_band_description = const_string_output(std_call('GDALGetDescription'), [c_void_p])
 get_band_ds = voidptr_output(std_call('GDALGetBandDataset'), [c_void_p])
 get_band_datatype = int_output(std_call('GDALGetRasterDataType'), [c_void_p])
+get_band_color_interp = int_output(std_call('GDALGetRasterColorInterpretation'), [c_void_p])
 get_band_nodata_value = double_output(std_call('GDALGetRasterNoDataValue'), [c_void_p, POINTER(c_int)])
 set_band_nodata_value = void_output(std_call('GDALSetRasterNoDataValue'), [c_void_p, c_double])
 if GDAL_VERSION >= (2, 1):

django/contrib/gis/gdal/raster/band.py

@@ -6,7 +6,9 @@ from django.contrib.gis.gdal.raster.base import GDALRasterBase
 from django.contrib.gis.shortcuts import numpy
 from django.utils.encoding import force_text
 
-from .const import GDAL_INTEGER_TYPES, GDAL_PIXEL_TYPES, GDAL_TO_CTYPES
+from .const import (
+    GDAL_COLOR_TYPES, GDAL_INTEGER_TYPES, GDAL_PIXEL_TYPES, GDAL_TO_CTYPES,
+)
 
 
 class GDALBand(GDALRasterBase):
@@ -168,6 +170,13 @@ class GDALBand(GDALRasterBase):
             dtype = GDAL_PIXEL_TYPES[dtype]
         return dtype
 
+    def color_interp(self, as_string=False):
+        """Return the GDAL color interpretation for this band."""
+        color = capi.get_band_color_interp(self._ptr)
+        if as_string:
+            color = GDAL_COLOR_TYPES[color]
+        return color
+
     def data(self, data=None, offset=None, size=None, shape=None, as_memoryview=False):
         """
         Read or writes pixel values for this band. Blocks of data can

django/contrib/gis/gdal/raster/const.py

@@ -44,6 +44,27 @@ GDAL_RESAMPLE_ALGORITHMS = {
     'Mode': 6,
 }
 
+# See http://www.gdal.org/gdal_8h.html#ace76452d94514561fffa8ea1d2a5968c
+GDAL_COLOR_TYPES = {
+    0: 'GCI_Undefined',  # Undefined, default value, i.e. not known
+    1: 'GCI_GrayIndex',  # Greyscale
+    2: 'GCI_PaletteIndex',  # Paletted
+    3: 'GCI_RedBand',  # Red band of RGBA image
+    4: 'GCI_GreenBand',  # Green band of RGBA image
+    5: 'GCI_BlueBand',  # Blue band of RGBA image
+    6: 'GCI_AlphaBand',  # Alpha (0=transparent, 255=opaque)
+    7: 'GCI_HueBand',  # Hue band of HLS image
+    8: 'GCI_SaturationBand',  # Saturation band of HLS image
+    9: 'GCI_LightnessBand',  # Lightness band of HLS image
+    10: 'GCI_CyanBand',  # Cyan band of CMYK image
+    11: 'GCI_MagentaBand',  # Magenta band of CMYK image
+    12: 'GCI_YellowBand',  # Yellow band of CMYK image
+    13: 'GCI_BlackBand',  # Black band of CMLY image
+    14: 'GCI_YCbCr_YBand',  # Y Luminance
+    15: 'GCI_YCbCr_CbBand',  # Cb Chroma
+    16: 'GCI_YCbCr_CrBand',  # Cr Chroma, also GCI_Max
+}
+
 # Fixed base path for buffer-based GDAL in-memory files.
 VSI_FILESYSTEM_BASE_PATH = '/vsimem/'
 

docs/ref/contrib/gis/gdal.txt

@@ -1551,6 +1551,22 @@ blue.
         ``GDT_UInt32``, ``GDT_Int32``, ``GDT_Float32``, ``GDT_Float64``,
         ``GDT_CInt16``, ``GDT_CInt32``, ``GDT_CFloat32``, and ``GDT_CFloat64``.
 
+    .. method:: color_interp(as_string=False)
+
+        .. versionadded:: 2.0
+
+        The color interpretation for the band, as an integer between 0and 16.
+        If ``as_string`` is ``True``, the data type is returned as a string
+        with the following possible values:
+        ``GCI_Undefined``, ``GCI_GrayIndex``, ``GCI_PaletteIndex``,
+        ``GCI_RedBand``, ``GCI_GreenBand``, ``GCI_BlueBand``, ``GCI_AlphaBand``,
+        ``GCI_HueBand``, ``GCI_SaturationBand``, ``GCI_LightnessBand``,
+        ``GCI_CyanBand``, ``GCI_MagentaBand``, ``GCI_YellowBand``,
+        ``GCI_BlackBand``, ``GCI_YCbCr_YBand``, ``GCI_YCbCr_CbBand``, and
+        ``GCI_YCbCr_CrBand``. ``GCI_YCbCr_CrBand`` also represents ``GCI_Max``
+        because both correspond to the integer 16, but only ``GCI_YCbCr_CrBand``
+        is returned as a string.
+
     .. method:: data(data=None, offset=None, size=None, shape=None)
 
         The accessor to the pixel values of the ``GDALBand``. Returns the complete

docs/releases/2.0.txt

@@ -144,6 +144,10 @@ Minor features
   GDAL's internal virtual filesystem. Rasters can now be :ref:`created from and
   converted to binary data <gdal-raster-vsimem>` in-memory.
 
+* The new :meth:`GDALBand.color_interp()
+  <django.contrib.gis.gdal.GDALBand.color_interp>` method returns the color
+  interpretation for the band.
+
 :mod:`django.contrib.messages`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tests/gis_tests/gdal_tests/test_raster.py

@@ -562,6 +562,8 @@ class GDALBandTests(SimpleTestCase):
         self.assertEqual(self.band.description, '')
         self.assertEqual(self.band.datatype(), 1)
         self.assertEqual(self.band.datatype(as_string=True), 'GDT_Byte')
+        self.assertEqual(self.band.color_interp(), 1)
+        self.assertEqual(self.band.color_interp(as_string=True), 'GCI_GrayIndex')
         self.assertEqual(self.band.nodata_value, 15)
         if numpy:
             data = self.band.data()