[FWTools] Trying to translate gtif ASTER image to jpg but v. slow

Simon J. Hook simon.j.hook at jpl.nasa.gov
Tue Feb 6 14:46:18 EST 2007

I added the --config to the call line and WOW it took 2 secs - that is 
what I call a performance improvement. One further quick question. Can I 
automatically change the extension of the jpg world file to .jgw. For 
some reason ENVI does not recognize .wld, I can rename the file in my 
script if necessary.

Thanks again.


Frank Warmerdam wrote:
> Simon J. Hook wrote:
>> Hi Frank,
>> I have put the file on my ftp site. It requires a username and 
>> password to retrieve so I have not sent this message to the FWTools 
>> list (I hope that is okay). I tried running it with the new FWTools 
>> (1.2) on a v. fast machine (dual 3ghz, 4gb ram). Our code which 
>> generates the geotif from the ASTER image took about 15 secs. The 
>> gdal code which generated the jpg from the geotif took about 14.5 
>> mins. Interestingly before I ran it on my laptop (much slower 
>> machine), before so having more cpu does not seem to help.
>> Here is the command I ran
>> gdal_translate -of JPEG -co WORLDFILE=ON ml_VNIR_geo.tif ml.jpg
> Simon,
> A gdalinfo on the file reports:
> Band 1 Block=5796x4888 Type=Byte, ColorInterp=Gray
> Band 2 Block=5796x4888 Type=Byte, ColorInterp=Undefined
> Band 3 Block=5796x4888 Type=Byte, ColorInterp=Undefined
> The key item is the block size.  The files are treated as a single big
> strip.
> So what happens is that the entire TIFF file needs to be re-read to
> satisfy each scanline of jpeg output since any single tile is larger
> than the default cache size.  A worst possible case of cache thrashing.
> But if I set the cache max converting the file only takes 2.8 seconds of
> wall clock time on my machine:
> warmerda at amd64[127]% time gdal_translate --config GDAL_CACHEMAX 200 
> -of JPEG ml_VNIR_geo.tif out.jpg
> GDAL: GDALOpen(ml_VNIR_geo.tif) succeeds as GTiff.
> Input file size is 5796, 4888
> 0...10...20...30...40...50...60...70...80...90...100 - done.
> GDAL: GDALOpen(out.jpg) succeeds as JPEG.
> GDAL: GDALClose(out.jpg)
> GDAL: GDALClose(ml_VNIR_geo.tif)
> GDAL: GDALDeregister_GTiff() called.
> 2.452u 0.316s 0:02.82 97.8%     0+0k 0+0io 0pf+0w
> You mentioned earlier that you tried:
> >
> > gdal_translate --config GDAL_CACHEMAX 512
> >
> > and then ran the gdal_translate but it is still v. sloow.
> Did you actually include the --config request in the run of 
> gdal_translate
> with the data?  The --config switch only sets the configuration option 
> for
> the period of the program running - it doesn't set something persistent.
> Best regards,

Simon J. Hook, MSc, PhD
Discipline Program Manager, Carbon Cycle and Ecosystems
MS 183-501, Jet Propulsion Laboratory
4800 Oak Grove Drive  
Pasadena, CA 91109
Office: 818-354-0974
Mobile: 818-640-8344
Fax: 818-354-0966
Email: simon.j.hook at jpl.nasa.gov

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