[gdal-dev] Large image support

[Frank Warmerdam]

ldjohn at u... wrote:

> Hello Frank,
> 
> Looking through the GDAL mailing list archive, I noticed that on January
> 3, 2001 you sent a message saying that you have added support for large
> images (> 2GB), but that the changes haven't (at that time anyway) been
> made to the raw image format. I haven't seen any follow-ups on this
> message, and from the testing I've done, it appears that the RawDataset
> class doesn't yet support such large images.
> 
> The LAS package (which my group supports) is being used more and more to
> process large area mosaics and Landsat 7 scenes, so one of our
> requirements is the support of large (> 2GB per band, multiple bands per
> image) images. As we prepare to switch our image I/O layer to GDAL, I
> need to ensure that such large images can be handled.
> 
> The LDFDataset (LAS Data Format) class is being built upon the RawDataset
> class. Does the RawDataset class remain to be changed to handle large
> images? Let me know if I can help with the process.


Lowell,

The large file IO api is available in GDAL, but an alternate set of
functions is called, and the file handles are not necessary interchangeable
(not on NT for instance).

Because a variety of things build on the RawDataset (or more specifically
the RawRasterBand), and that some of them have their own code to access the
file through the file handle, I think it would be best for me to add an
alternate LargeRawRasterBand which operates on large file style file handles.

I will implement this and incorporate it's use into the default raw file
handler. Then you should be able to just change LDFRasterBand to
derive from LargeRawRasterBand instead of RawRasterBand.

Best regards,

-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at p...
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent