Convert complex types to float when it comes to nodata

Resolves #1747

CHANGES.txt

@@ -4,6 +4,7 @@ Changes
 1.0.26 (TBD)
 ------------
 
+- Allow complex datasets to be created with a specified nodata value (#1747).
 - When a MemoryFile is opened in write mode, a TypeError will be raised if
   integer width and height are not given, fixing #1748.
 

rasterio/_base.pyx

@@ -420,6 +420,13 @@ cdef class DatasetBase(object):
             for i in range(self._count):
                 band = self.band(i + 1)
                 dtype = _band_dtype(band)
+
+                # To address the issue in #1747.
+                if dtype == "complex128":
+                    dtype = "float64"
+                elif dtype == "complex64":
+                    dtype = "float32"
+
                 nodataval = GDALGetRasterNoDataValue(band, &success)
                 val = nodataval
                 # GDALGetRasterNoDataValue() has two ways of telling you that

tests/test_complex_dtypes.py

@@ -36,3 +36,25 @@ def test_read_array(tempfile, dtype, height, width):
         dataset.write(in_img, 1)
         out_img = dataset.read(1)
     assert (in_img == out_img).all()
+
+
+def test_complex_nodata(tmpdir):
+    """A complex dataset can be created with a real nodata value"""
+    import numpy as np
+    import rasterio
+    from rasterio.transform import Affine
+
+    x = np.linspace(-4.0, 4.0, 240)
+    y = np.linspace(-3.0, 3.0, 180)
+    X, Y = np.meshgrid(x, y)
+    Z1 = np.ones_like(X) + 1j
+
+    res = (x[-1] - x[0]) / 240.0
+    transform1 = Affine.translation(x[0] - res / 2, y[-1] - res / 2) * Affine.scale(res, -res)
+
+    tempfile = str(tmpdir.join("test.tif"))
+    with rasterio.open(tempfile, 'w', driver='GTiff', height=Z1.shape[0], width=Z1.shape[1], nodata=0, count=1, dtype=Z1.dtype, crs='+proj=latlong', transform=transform1) as dst:
+        dst.write(Z1, 1)
+
+    with rasterio.open(tempfile) as dst:
+        assert dst.nodata == 0