[Qgis-user] Metis and creating pyramids

[Maciej Sieczka]

Micha Silver pisze:
> I can't seem to create pyramids with 0.11. Neither on Windows nor on
>  Ubuntu.
> 
> I'm working with some tif rasters, of about 160 MB each. They were 
> originally jpeg, which I converted with gdal_translate. The jpegs
> load *very* slowly. They are about 10 MB, and it takes some 45 secs
> to load each image. After converting to three-band tiffs:
> 
> gdal_translate -of GTiff -co 'TILED=YES' file.jpg file.tif I can load
> the tiff in about 15 secs. (Just for comparison, the same 10MB jpeg
> images load in ArcMap in about 5 secs, and the 160 MB tiff, after Arc
> creates their external pyramids, loads almost immediately...)

Regarding rendering perfomance - try to create a TIFF without tiles
(gdal_translate -co "TILED=NO" -co "BLOCKYSIZE=1"). At least for me,
stripped TIFF is loaded almost instantly compared to a tiled one - 1.605
sec vs 15.098 sec for a 361 MB TIFF without compression (FWIW, te same
raster as JPEG loads in over 25 sec).

However, after building pyramids for tiled and stripped TIFF, both
render about same quick for me (tiled slightly faster actually, but only
by decimal parts of a second).

Anybody knows why QGIS renders tiled rasters without pyramids so slow?

> 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.
> 
> Can anyone else confirm this?

For me building pyramids in QGIS works OK.

Maciek

-- 
Maciej Sieczka
www.sieczka.org