gdal2tiles.py patch for managing empty tiles

[Kurt Schwehr]

Another Google engineer, Hideto Kazawa, found that gdal2tiles.py crashes for empty tiles.

swig/python/scripts/gdal2tiles.py -z 7-21 debug.tif tmp
Generating Base Tiles:
ERROR 5: Illegal values for buffer size
ERROR 5: Illegal values for buffer size
Traceback (most recent call last):
  File "./swig/python/scripts/gdal2tiles.py", line 2272, in <module>
    gdal2tiles.process()
  File "./swig/python/scripts/gdal2tiles.py", line 481, in process
    self.generate_base_tiles()
  File "./swig/python/scripts/gdal2tiles.py", line 1282, in generate_base_tiles
    dsquery.WriteRaster(wx, wy, wxsize, wysize, data, band_list=list(range(1,self.dataBandsCount+1)))
  File "/home/schwehr/src/gdal/inst/lib/python2.7/site-packages/GDAL-2.1.0-py2.7-linux-x86_64.egg/osgeo/gdal.py", line 856, in WriteRaster
    buf_pixel_space, buf_line_space, buf_band_space )
TypeError: not a string

He proposes this patch. It looks okay to me, but I could use a double check. Does this look reasonable? If there aren't any concerns, I'll go ahead and apply it to trunk.

swig/python/scripts/gdal2tiles.py

@@ -1257 +1257 @@
                 if self.options.verbose:
                     print("\tReadRaster Extent: ", (rx, ry, rxsize, rysize), (wx, wy, wxsize, wysize))
 
+                if wxsize == 0 or wysize == 0:
+                    continue
+
                 # Query is in 'nearest neighbour' but can be bigger in then the tilesize
                 # We scale down the query to the tilesize by supplied algorithm.
 
@@ -1364 +1367 @@
                         for x in range(2*tx,2*tx+2):
                             minx, miny, maxx, maxy = self.tminmax[tz+1]
                             if x >= minx and x <= maxx and y >= miny and y <= maxy:
-                                dsquerytile = gdal.Open( os.path.join( self.output, str(tz+1), str(x), "%s.%s" % (y, self.tileext)), gdal.GA_ReadOnly)
+                                tilefile = os.path.join(self.output, str(tz+1), str(x), "%s.%s" % (y, self.tileext))
+                                if not os.path.exists(tilefile):
+                                    continue
+                                dsquerytile = gdal.Open(tilefile , gdal.GA_ReadOnly)
+                                if dsquerytile is None:
+                                   continue
                                 if (ty==0 and y==1) or (ty!=0 and (y % (2*ty)) != 0):
                                     tileposy = 0
                                 else:

[Kurt Schwehr]

File that crashes gdal2tiles.py -z 7-21 debug.tif tmp

[Jukka Rahkonen]

Is this about the same thing as tickets #3596 and #5005?

[Even Rouault]

Replying to jratike80:

Is this about the same thing as tickets #3596 and #5005?

Yes, same patch as ​https://trac.osgeo.org/gdal/attachment/ticket/5005/gdal2tiles.patch #3596 is about empty/transparent content in tiles, whereas this one is about 0xX ou Xx0 tiles.

Looks good to me.

What would be most appreciated is a autotest/pyscripts/test_gdal2tiles.py script since we have none currently.

[Kurt Schwehr]

I will try to create a test and get the test and patch in soon.

[Even Rouault]

Also reported as #6106

[Even Rouault]

In 37210:

gdal2tiles: do not crash on empty tiles generation (patch by Gregory Bataille, fixes #6057, github #188)

Due to raster border approximation where the border coords is in a tile A while the border pixel is
in a tile B, neighbour of A