[gdal-dev] How do I select 3 of 5 bands for output?

[Stephen Woodbridge]

Stephen Woodbridge wrote:
> Lucena, Ivan wrote:
>> Hi Steve,
>>
>>>  I have a script that was processing MrSID files and need to convert it
>>>  to support jp2 files also. It seems pretty straight forward except the
>>>  jp2 files have bands R,G,B,IR and I need to chop these into GeoTif 
>>> tiles
>>>  with only R,G,B bands.
>>>  
>>>  The script was iterating over the src image and chopping it into tiles
>>>  using the following command:
>>>  
>>>  system("gdalwarp -srcnodata 0 -dstnodata 0 -s_srs +init=epsg:$epsg
>>>  -t_srs EPSG:4326 -te $xm $ym $xx $yx -rb -wm 250 --config
>>>  GDAL_ONE_BIG_READ ON -co "TILED=YES" $infile $work/$outd/$outf\n");
>>>  
>>>  1) How does this behave with R,G,B,IR as input and how can I get R,G,B
>>>  only into the GeoTif?
>>
>> I would add one call to gdal_translate with "-b 1 -b 2 -b 3" first to 
>> build a VRT and then call gdalwarp from the VRT.
>>
>> {
>>   system("gdaltranslate $infile -b 1 -b 2 -b 3 tmp.vrt");
>>   system("gdalwarp -srcnodata 0 -dstnodata 0 -s_srs +init=epsg:$epsg 
>> -t_srs EPSG:4326 -te $xm $ym $xx $yx -rb -
>> wm 250 --config GDAL_ONE_BIG_READ ON -co "TILED=YES" tmp.vrt 
>> $work/$outd/$outf\n");
>> }
>> system("gdalmanage delete tmp.vrt");
> 
> OK, this might work, but it is incredibly slow. Then again probably 
> doing much of anything with these images will be slow because they are 
> HUGE. So looking for ways to speed this up. It looks like the .vrt file 
> is really a GeoTif would it help later if the .vrt was made with -co 
> "TILED=YES", can you do this with a .vrt file. I think the uncompressed 
> 3 band geoTif will be in the ballpark of 10GB, is this being made as a 
> BigTiff? or will I run into problems when I hit the 2GB limit?
> 
> Anyway to get this to go faster? CPU is at 101%, 78MB of memory is being 
> used, I have LOTS more if I can get gdal to use it.

OK, it took 2 hr 10 min to run:

GDAL_SKIP=JPEG2000 gdal_translate
/var/data/raw_data/minnesota/ortho_1-1_1m_j_mn161_2008_1.jp2  -b 1 -b 2
-b 3 tmp.vrt

and the output file is 5.0 GB. And on top of this I still need to
gdalwarp this VRT file a bunch of times to chop it into smaller tiles. I
have hundreds of files to process. Any thoughts on how to speed this up?

-Steve