[gdal-dev] Test and a question about gdal_warp and gdal_translate

[Frank Warmerdam]

On 11-01-12 04:30 PM, Antonio P wrote:
> Hello again : ( I dont know if my question was sent to the list ....)

Antonio,

I believe it already went through and there were some responses.
You can check the list archives after a bit to see if a message has
gone through.

> I cannot use gdal_translate with % outsize parameters :
> gdal_translate -of JPEG -outsize 25% 25% DSC02699.jpg 02699.jpg
>  >> does nothing (I view the use options of gdal_translate, it seems as I wrote
> a wrong parameter )
> gdal_translate -of JPEG -outsize 25 25 DSC02699.jpg 02699.jpg works ok (I get a
> 25 x25 pixels image)
> I use gdal 7.7.0b2 provided by FWTools 2.4.7

You still haven't answered the easier question about what "does nothing"
means in the regard.  But I'm guessing you will have problems using
percentage characters on the commandline on windows without some sort
of escaping or quoting.  % normally instructs Window's CMD.EXE to
substitute in an environment variable.

> Any idea ?
> Also , I 'd like to use gdal_warp simply to rescale an image to 50% 50% ? Can
> anyone tell me the command line syntax ?

I do not believe there is an equivelent to the percentage thing. But
you can request a particular output size in pixels and lines using
-ts.  Just use gdalinfo to find the size of the input image in pixels
and lines, and divide by two and use them with -ts.

eg.
gdalwarp -ts 1000 1000 in.tif out.tif


> (i'd like to use resampling options ...)
> And .... I miss more information, more examples or more tutorials on how to use
> the command line utilities. Any good link ?
> Thanks , Antonio

There is some useful information at:

   http://trac.osgeo.org/gdal/wiki/UserDocs

Good luck,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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