[gdal-dev] Error when trying to compress a TIFF file

[Hanlie Pretorius]

Thanks, the r- average option improved the quality quite a bit.

2014-08-26 17:34 MGT+02:00, Even Rouault <even.rouault at spatialys.com>:
> Selon Hanlie Pretorius <hanlie.pretorius at gmail.com>:
>
>> Hi Even,
>>
>> Thanks, the gdaldo command made a huge difference to the speed with
>> which QGIS works with the raster.
>>
>> The image looks a bit shoddy, though, even when zoomed out. It
>> improved when I set the quality to 100 and the file is still a tenth
>> of the original size.
>
> You can try adding -r average or -r cubic when computing overviews with
> gdaladdo
> to improve a bit their quality.
>
>>
>> Would it help to create more levels in the overview and, if so, at
>> which end should I add the levels?
>
> Your full-res image is around 30000 x 30000.
> With a max overview of factor 16 as in the below command, you have an image
> of
> approximate size 1800x1800, which is still a bit big
> Targetting 256x256 for the smallest overview would bring you instantaneous
> opening in QGIS. So 30000 / 256 = 117.XXXX, round that to 128. So use "2 4 8
> 16
> 32 64 128".
>
>>