AW: [mapserver-users] visualisation of image with overviews

[Fischer, Andreas]

Hi Toni,
I think gdal_translate is not able to save overviews once you produced them with gdaladdo before. Therefore you do have to use gdaladdo after you are done with all the other stuff. But as far as I know you can't do both: Use Internal Tiling and overviews, because gdaladdo does not support the creation option for internal tiling. I don't know what gdal_translate does with the internal overviews once they are created, maybe the one with the lowest resolution is saved. ;-)

I did a lot of downsampling aerial images using gdalwarp with -rc. for creating 'external overviews'. This way I did always get very good results and I can use internal tiling too. For the mapfile I calculate proper scales depending on input image resolution and the resolution of the presentation (e.g. max scale = 20cm/dot input image x 28 dpc (72dpi) /or 38 dpc (96dpi). For sure in any case of resampling arial images you do need 24bit images.

This might cause more effort, but in my opinion the results are good and fast.

Best regards
Andreas

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Andreas Fischer

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-----Ursprüngliche Nachricht-----
Von: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] Im Auftrag von Toni Pignataro
Gesendet: Freitag, 11. Februar 2011 15:51
An: mapserver-users at lists.osgeo.org
Betreff: [mapserver-users] visualisation of image with overviews

Hi list,

I have a  nonsatisfying visualisation of an geotiff image with overviews 
in mapserver. The different overviews look really poor zooming in the map.

What i tried until now is, resampling the original image with gdal_addo 
(gdaladdo -r nearest , gdaladdo -r average_mp, gdaladdo -r 
average_magphase, gdaladdo -r mode) and i also made an gdal_translate 
(gdal_translate -of GTiff -co "TILLED=YES"), but the results did not 
look even better.

Any one an suggestion how to handle the orginalimage?


Thanks,
Toni




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