Added RasterSource/GDALBand GDAL objects

Based on Daniel Wiesmann's raster branch. Thanks Daniel Wiesmann
and Tim Graham for the reviews. Refs #23804.

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

@@ -0,0 +1,155 @@
+from ctypes import addressof, byref, c_double
+import os
+
+from django.contrib.gis.gdal.base import GDALBase
+from django.contrib.gis.gdal.driver import Driver
+from django.contrib.gis.gdal.error import GDALException
+from django.contrib.gis.gdal.prototypes import raster as capi
+from django.contrib.gis.gdal.raster.band import GDALBand
+from django.contrib.gis.gdal.srs import SpatialReference, SRSException
+from django.utils import six
+from django.utils.six.moves import range
+from django.utils.encoding import (force_bytes, force_text,
+    python_2_unicode_compatible)
+from django.utils.functional import cached_property
+
+
+class TransformPoint(list):
+    indices = {
+        'origin': (0, 3),
+        'scale': (1, 5),
+        'skew': (2, 4),
+    }
+
+    def __init__(self, raster, prop):
+        x = raster.geotransform[self.indices[prop][0]]
+        y = raster.geotransform[self.indices[prop][1]]
+        list.__init__(self, [x, y])
+        self._raster = raster
+        self._prop = prop
+
+    @property
+    def x(self):
+        return self[0]
+
+    @property
+    def y(self):
+        return self[1]
+
+
+@python_2_unicode_compatible
+class GDALRaster(GDALBase):
+    """
+    Wraps a raster GDAL Data Source object.
+    """
+    def __init__(self, ds_input, write=False):
+        self._write = 1 if write else 0
+        Driver.ensure_registered()
+
+        # If input is a valid file path, try setting file as source.
+        if isinstance(ds_input, six.string_types):
+            if os.path.exists(ds_input):
+                try:
+                    # GDALOpen will auto-detect the data source type.
+                    self.ptr = capi.open_ds(force_bytes(ds_input), self._write)
+                except GDALException as err:
+                    raise GDALException('Could not open the datasource at "{}" ({}).'.format(
+                        ds_input, err))
+            else:
+                raise GDALException('Unable to read raster source input "{}"'.format(ds_input))
+        else:
+            raise GDALException('Invalid data source input type: "{}".'.format(type(ds_input)))
+
+    def __del__(self):
+        if self._ptr and capi:
+            capi.close_ds(self._ptr)
+
+    def __str__(self):
+        return self.name
+
+    def __repr__(self):
+        """
+        Short-hand representation because WKB may be very large.
+        """
+        return '<Raster object at %s>' % hex(addressof(self.ptr))
+
+    @property
+    def name(self):
+        return force_text(capi.get_ds_description(self.ptr))
+
+    @cached_property
+    def driver(self):
+        ds_driver = capi.get_ds_driver(self.ptr)
+        return Driver(ds_driver)
+
+    @property
+    def width(self):
+        """
+        Width (X axis) in pixels.
+        """
+        return capi.get_ds_xsize(self.ptr)
+
+    @property
+    def height(self):
+        """
+        Height (Y axis) in pixels.
+        """
+        return capi.get_ds_ysize(self.ptr)
+
+    @property
+    def srs(self):
+        """
+        Returns the Spatial Reference used in this GDALRaster.
+        """
+        try:
+            wkt = capi.get_ds_projection_ref(self.ptr)
+            return SpatialReference(wkt, srs_type='wkt')
+        except SRSException:
+            return None
+
+    @cached_property
+    def geotransform(self):
+        """
+        Returns the geotransform of the data source.
+        Returns the default geotransform if it does not exist or has not been
+        set previously. The default is (0.0, 1.0, 0.0, 0.0, 0.0, -1.0).
+        """
+        # Create empty ctypes double array for data
+        gtf = (c_double * 6)()
+        capi.get_ds_geotransform(self.ptr, byref(gtf))
+        return tuple(gtf)
+
+    @property
+    def origin(self):
+        return TransformPoint(self, 'origin')
+
+    @property
+    def scale(self):
+        return TransformPoint(self, 'scale')
+
+    @property
+    def skew(self):
+        return TransformPoint(self, 'skew')
+
+    @property
+    def extent(self):
+        """
+        Returns the extent as a 4-tuple (xmin, ymin, xmax, ymax).
+        """
+        # Calculate boundary values based on scale and size
+        xval = self.origin.x + self.scale.x * self.width
+        yval = self.origin.y + self.scale.y * self.height
+        # Calculate min and max values
+        xmin = min(xval, self.origin.x)
+        xmax = max(xval, self.origin.x)
+        ymin = min(yval, self.origin.y)
+        ymax = max(yval, self.origin.y)
+
+        return xmin, ymin, xmax, ymax
+
+    @cached_property
+    def bands(self):
+        bands = []
+        for idx in range(1, capi.get_ds_raster_count(self.ptr) + 1):
+            bands.append(GDALBand(self, idx))
+        return bands