[gdal-dev] Using MEM driver to output to an gtiff in /vsimem/

[Even Rouault]

Le mercredi 30 mars 2011 00:17:17, Bborie Park a écrit :
> Hi,
> 
> What I'm attempting to do is write some code to do the following:
> 
> PostGIS Raster -> GDAL MEM -> user specified GDAL output format in
> /vsimem/ (e.g. GTiff) -> return contents of the output file to user
> 
> I'm able to successfully create a MEM dataset with raw band data
> specified using the DATAPOINTER creation option and the GDALRasterIO()
> function from a PostGIS Raster.  I've been successful outputting the MEM
> dataset using CreateCopy() to a GTiff stored on the filesystem (e.g.
> /tmp/out.tif), such as...
> 
> rtn_ds = GDALCreateCopy(
> 	rtn_drv,
> 	"/tmp/out.tif",
> 	src_ds,
> 	FALSE,
> 	options,
> 	NULL,
> 	NULL
> );
> 
> What does not seem to work is if I use CreateCopy with a /vsimem/ path.
> 
> rtn_ds = GDALCreateCopy(
> 	rtn_drv,
> 	"/vsimem/out.tif",
> 	src_ds,
> 	FALSE,
> 	options,
> 	NULL,
> 	NULL
> );

--> Here, you must close the dataset so it to be properly flushed before 
getting the buffer.

> 
> rtn = VSIGetMemFileBuffer("/vsimem/out.tif", &j, FALSE);
> 
> When I read /vsimem/out.tif back out to pass back to the end-user, the
> contents are significantly shorter than what it should be.  From what I
> can tell, the contents outputted are just the tiff header information
> and none of the band data.
> 
> Is there something different about outputting a raster to a filesystem
> rather than /vsimem/ when working with a MEM raster with external band
> data?
> 
> Thanks,
> Bborie