rpc_from_geotiff fails if there is a textual RPC.txt next to the tiff

rpcm/rpc_model.py

@@ -62,6 +62,22 @@ def apply_rfm(num, den, x, y, z):
     return apply_poly(num, x, y, z) / apply_poly(den, x, y, z)
 
 
+def remove_ikonos_units(rpc_dict):
+    """
+    When there is a RPC.txt file along the tif, GDAL will get the rpcs from
+    the textual file instead of the tif.
+    However, ikonos textual files contain units along the numbers, and these
+    are not expected when constructing from GeoTiff.
+    This function removes the units from the dict.
+    """
+    geotiff_dict = {}
+    for key, value in rpc_dict.items():
+        if key.endswith('_OFF') or key.endswith('_SCALE'):
+            value = value.split()[0]
+        geotiff_dict[key] = value
+    return geotiff_dict
+
+
 def rpc_from_geotiff(geotiff_path):
     """
     Read the RPC coefficients from a GeoTIFF file and return an RPCModel object.
@@ -73,7 +89,7 @@ def rpc_from_geotiff(geotiff_path):
         instance of the rpc_model.RPCModel class
     """
     with rasterio.open(geotiff_path, 'r') as src:
-        rpc_dict = src.tags(ns='RPC')
+        rpc_dict = remove_ikonos_units(src.tags(ns='RPC'))
     return RPCModel(rpc_dict)
 
 

tests/test_rpc_constructors.py

@@ -1,22 +1,66 @@
 import os
-
-from rpcm import RPCModel
+import shutil
+import numpy as np
+import pytest
+from rpcm import RPCModel, rpc_from_geotiff
+from rpcm.utils import rasterio_write
 from rpcm.rpc_file_readers import read_rpc_file
 
 here = os.path.abspath(os.path.dirname(__file__))
 files_dir = os.path.join(here, "test_rpc_files")
 
 
+def _read_dict_from_file(filename="rpc_IKONOS.txt"):
+    filepath = os.path.join(files_dir, filename)
+    return read_rpc_file(filepath)
+
+
 def test_rpc_constructors():
     """
     Test that the two constructors of the RPCModel class yield the same object.
     """
-    filepath = os.path.join(files_dir, "rpc_IKONOS.txt")
-
-    geotiff_dict = read_rpc_file(filepath)
+    geotiff_dict = _read_dict_from_file("rpc_IKONOS.txt")
     geotiff_rpc = RPCModel(geotiff_dict, dict_format="geotiff")
 
     rpcm_dict = geotiff_rpc.__dict__
     rpcm_rpc = RPCModel(rpcm_dict, dict_format="rpcm")
 
     assert geotiff_rpc == rpcm_rpc
+
+
+@pytest.fixture
+def tmp_geotiff(tmp_path):
+    """
+    provides a geotiff with some rpcs, stored in the tmp_path
+    """
+    data = np.ones([1, 10, 10], dtype=np.uint8)
+    rpc = RPCModel(_read_dict_from_file())
+    tags = dict(ns="RPC", **rpc.to_geotiff_dict())
+
+    geotiff_path = os.fspath(tmp_path / "test_geo.tif")
+    rasterio_write(geotiff_path, data, tags=tags)
+    return geotiff_path
+
+
+def _add_auxiliary_rpc_file(tif_path, rpc_filename="rpc_IKONOS.txt"):
+    """
+    Adds an RPC textfile {basename}_RPC.txt, next to the given `tif_path`
+    (with filename {basename}.tif).
+    GDAL recognizes such files, and automatically reads the information from
+    them as if it was stored inside the tif tags.
+    """
+    src = os.path.join(files_dir, rpc_filename)
+    dst = tif_path[:-len(".tif")] + "_RPC.txt"
+    shutil.copyfile(src, dst)
+
+
+def test_from_geotiff(tmp_geotiff, tmp_path):
+    # Verify that RPCs read from a geotiff match the textual file
+    txt_rpc = RPCModel(_read_dict_from_file())
+    tif_rpc = rpc_from_geotiff(tmp_geotiff)
+    assert tif_rpc == txt_rpc
+
+    # verify that RPCs from geotiff work if there is an auxiliary file
+    _add_auxiliary_rpc_file(tmp_geotiff)
+    tif_rpc = rpc_from_geotiff(tmp_geotiff)
+    assert tif_rpc == txt_rpc