[Qgis-user] Metis and creating pyramids
tutey at o2.pl
Mon Jul 28 13:25:40 EDT 2008
Micha Silver pisze:
> Maciej Sieczka wrote:
>> Regarding rendering perfomance - try to create a TIFF without tiles
>> (gdal_translate -co "TILED=NO" -co "BLOCKYSIZE=1").
> Many thanks! Your suggestion certainly helped. It seems that giving
> the explicit "TILED=NO" option creates a stripped tiff that loads
> *much* faster. And zooming was very good also. (BTW I didn't use
> BLOCKYSIZE=1 as that gave an error ).
It shouldn't. It's a valid TIFF creation option . What error exactly?
> In the gdal_translate docs it says that the default (with no TILED=
> option) is stripped tiff, but that doesn't seem to be the case?
Stripped TIFF is a default gdal_translate output for me. What GDAL
version (I'm using GDAL 1.5.2 + SVN r15027)?
> When I created tiffs with no TILED option they loaded quite slowly.
> Then I added the TILED=YES, and still the images loaded and zoomed
> slowly. TILED=NO gave a dramatic improvement.
>> Anybody knows why QGIS renders tiled rasters without pyramids so
Hey, Developers! Any ideas?
>>> But when I try to create pyramids, it seems to be working for a
>>> while, then the process ends. But there is no change to the file,
>>> and if I reopen the properties window to the Pyramids tab, all
>>> pixel levels are still marked in red. The tiff's are in my
>>> homedir so, yes, I have write access.
>> For me building pyramids in QGIS works OK.
> I see that with stripped, non-tiled tiff's, I can create pyramids in
> QGIS with no problem. Previously, when I used TILED=YES in
> gdal_translate, the Create Pyramids didn't do anything. I suppose you
> wouldn't want or need both tiled tiff and pyramids so maybe it's a
> feature that zoom levels are not duplicated?
Tiles and overviews (pyramids) are two distinct things and not mutually
exclusive. Applying overviews to a tiled TIFF works for me in QGIS (as
well as for stripped TIFF) and improves it's render times greatly.
More information about the Qgis-user