[Gdal-dev] How to scale an image

[Frank Warmerdam]

Sonson Sonson wrote:
> Hi all,
> I have a question. I would like to know how to scale an image. I am
> writing a program where I need to scale an image before processing it,
> but I cannot find any sample program, or documentation on how to do
> that. Say if my image's size is 6579x3289 pixel and I want it to be
> scaled to 6656x3328, can anybody point me to documentation and sample
> codes on how to do it.

Sonson,

What sort of sampling approach do you want to take?  If you just
want nearest neighbour resampling you can do this as:

   gdal_translate -outsize 6656 3328 in.tif out.tif

or at the API level by specifying 6656,3328 as your buffer size when
doing a RasterIO() to read into memory.

If you want to control the resampling kernel you need to use the warp
api.  At the commandline:

   gdalwarp -rc in.tif out.tif -ts 6656 3328

At the API level it is fairly involved. You could review:

   http://www.gdal.org/warptut.html

Best regards,
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