[Gdal-dev] Newbie doubt: gdalwarp

[om]

Hi,

How can I scale a GeoTIFF image ?
I have tried
gdalwarp -tr 8000 8000 -ts 8000 8000 inputimage.tif out.tif        
(input image resolution is 5213x5613) and got the following error.

Creating output file that is 0P x 0L.
ERROR 1: Attempt to create 0x0x1 TIFF file, but width, height and bands
must be positive.

-Is it possible to scale the image using gdalwarp? or is there any other 
way I can accomplish this...
-or is it because I have done something stupid?

Thanks in advance

Om