ImageMosaic returning black images for missing tiles.

[Gordon Keith]

I have an ImageMosaic which is sparsely populated.
(Seabed bathymetry around Australia, 110E to 180E by 50S to 5S in
1degree x 1degree geotiffs, unsurprisingly there is no data for the land
or some of the ocean).

The GeoTiffs have transparency and overlays and if any data is
included in the request then the areas without data are transparent.

If the request area does not include any data, however the returned
image is opaque black.

It is possible to set it to return a transparent layer when no data is
included in the request?

Currently using geoserver 1.7.6.

Tiffs are generated using:

mbgrid -O $MAPNAME ...
listgeo $MAPNAME.tif > $MAPNAME.geo
convert -transparent white -depth 8 $MAPNAME.tif trans_$MAPNAME.tif
geotifcp -c lzw -g $MAPNAME.geo trans_$MAPNAME.tif $MAPNAME.tif
gdaladdo --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR --config INTERLEAVE_OVERVIEW PIXEL -r nearest $MAPNAME.tif 2 4 8 16 32 64



tiffinfo of a tiff image gives:

TIFFReadDirectory: Warning, bathy_150_151_-45_-44_bathy.tif: unknown field with tag 33550 (0x830e) encountered.
TIFFReadDirectory: Warning, bathy_150_151_-45_-44_bathy.tif: unknown field with tag 33922 (0x8482) encountered.
TIFFReadDirectory: Warning, bathy_150_151_-45_-44_bathy.tif: unknown field with tag 34735 (0x87af) encountered.
TIFFReadDirectory: Warning, bathy_150_151_-45_-44_bathy.tif: unknown field with tag 34737 (0x87b1) encountered.
TIFF Directory at offset 0x6dfc9e (7208094)
  Image Width: 4096 Image Length: 4096
  Resolution: 1024, 1024 pixels/inch
  Bits/Sample: 8
  Compression Scheme: LZW
  Photometric Interpretation: RGB color
  Extra Samples: 1<unassoc-alpha>
  FillOrder: msb-to-lsb
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 4
  Rows/Strip: 1
  Planar Configuration: single image plane
  DocumentName: trans_bathy_150_151_-45_-44_bathy.tif
  Software: ImageMagick 6.2.5 04/19/07 Q16 http://www.imagemagick.org
  Tag 33550: 0.000244,0.000244,0.000000
  Tag 33922: 0.000000,0.000000,0.000000,149.999878,-43.999878,0.000000
  Tag 34735: 1,1,0,4,1024,0,1,2,1025,0,1,2,1026,34737,29,0,2048,0,1,4326
  Tag 34737: Image generated by mbgrdtiff|
TIFF Directory at offset 0x6e7eb2 (7241394)
  Subfile Type: reduced-resolution image (1 = 0x1)
  Image Width: 2048 Image Length: 2048
  Tile Width: 128 Tile Length: 128
  Bits/Sample: 8
  Sample Format: unsigned integer
  Compression Scheme: LZW
  Photometric Interpretation: RGB color
  Extra Samples: 1<unassoc-alpha>
  Samples/Pixel: 4
  Planar Configuration: single image plane
TIFF Directory at offset 0x6e8770 (7243632)
...<last section repeating for each overlay>


Regards
Gordon

--

Gordon Keith
Programmer/Data Analyst
Marine Acoustics
CSIRO Marine and Atmospheric Research
http://www.cmar.csiro.au

There are 3 types of people, those who can count and those who can't.

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