Add Warp and Transform functionality for GDALRasters

[Daniel Wiesmann]

Warping and transforming (reprojecting) are fundamental operations on raster objects. Suporting those functions on GDALRaster objects makes the use of the raster api much more flexible.

[Daniel Wiesmann]

Created a pull request for the implementation. However, the patch still lacks testing and documentation.

​https://github.com/django/django/pull/4694

[Claude Paroz <claude@…>]

In c078021:

Refs #24840 -- Added GDALRaster Warp and transform methods

Thanks to Tim Graham for the review.

[Simon Charette]

Error on Oracle for the new gis_tests.gdal_tests.test_raster.GDALRasterTests.test_raster_transform ​test:

Traceback (most recent call last):
  File "/mnt/jenkinsdata/workspace/pull-requests-oracle/database/oracle11/python/python3.4/tests/gis_tests/gdal_tests/test_raster.py", line 266, in test_raster_transform
    ndv, ndv, 20, ndv, ndv, ndv, ndv,
AssertionError: Lists differ: [99, [118 chars]23, 99, 99, 99, 15, 21, 22, 99, 99, 99, 99, 20, 99, 99, 99, 64] != [99, [118 chars]23, 99, 99, 99, 15, 21, 22, 99, 99, 99, 99, 20, 99, 99, 99, 99]

First differing element 48:
64
99

  [99,
   99,
   99,
   99,
   4,
   99,
   99,
   99,
   99,
   2,
   3,
   9,
   99,
   99,
   99,
   1,
   2,
   8,
   13,
   19,
   99,
   0,
   6,
   6,
   12,
   18,
   18,
   24,
   99,
   10,
   11,
   16,
   22,
   23,
   99,
   99,
   99,
   15,
   21,
   22,
   99,
   99,
   99,
   99,
   20,
   99,
   99,
   99,
-  64]
+  99]

[Claude Paroz]

Apparently, this error can also occur with SQLite or Postgres, so it does not seem to be related to the database engine. I wasn't able to reproduce locally, though.

[Daniel Wiesmann]

Yes, this test uses the GDAL api only, so the failure is not related to the database. Maybe the gdal version? Where can I see the exact specification of the build environment?

[Tim Graham]

The Jenkins wiki page has details about installed versions.

[Daniel Wiesmann]

I was able to reproduce the same error on a fresh ubuntu precise where I installed the default gdal-bin, which turned out to be GDAL 1.7.3. So I guess the transform parameters or the sampling algorithm behave different for older gdal versions.

What is the best way to adapt to this? Add a flag to the test to check for the gdal version or find a test case that works for both?

[Claude Paroz]

Let's skip the test for older GDAL versions...

[Daniel Wiesmann]

Ok I narrowed down the gdal version, the test works from 1.8.1 forward (tested versions using ​this). Here is a patch for the version checker

​https://github.com/geodesign/django/commit/effdc27c60d670a5d393127e0d0be572fe5ec8ae

[Claude Paroz <claude@…>]

In b647ccfa:

Refs #24840 -- Added skip flag to raster transform test for GDAL<1.8.1.

Thanks to Simon Charette for the report.