[Qgis-user] Loading big images in QGIS: Erdas img vs. ecw vs. bigtiff

[Carlos Dávila]

Andreas Neumann escribió:
> Hello,
>
> I would like to discuss the loading of big images in QGIS: I have an
> aerial image with 56000 x 44000 pixel. I tried three different approaches.
> I wanted to just use one single file instead of tiles. I used gdal to
> prepare the images.
>
> Here are my results:
>
> * ECW:
>  - compresses fine
>  - 500mb limit doesn't seem to apply if I use the -co "LARGE_OK=YES"
>  - loads fine and fast with UMN
>  - loads very, very long in QGIS: >4 minutes
>  - once loaded zooming and panning is very quick
>   
On what O.S. are you running qgis? What qgis version? It takes over 10
minutes for me on debian using ecw files between 1-2 GB (tested with
different revisions after 0.9.1 release). Zooming, panning or toggle
vector layers edition takes the same time, not quick as you report. See
bug #778 (https://trac.osgeo.org/qgis/ticket/778) for more info.
> * Erdas imagine (HFA)
>  - spill files don't support compression, spill files have to be used if
> the filesize is bigger than 2GB
>  - loads very fast in QGIS, less than a second
>  - once loaded zooming and panning is slower compared with ecw
>
> * bigtiff: couldn't get this to work
>
> So, as a result I would, from a technical point of view, like to go with
> ecw, if the initial, very long loading time could be fixed in QGIS.
>
> So, here are my questions:
> - will I run into licensing problem with ecw?, esp. if my filesize is
> bigger than 500mb?
> - can the long loading times of the ecw files be fixed in qgis?
> - are there other better alternatives besides ecw/erdas imagine/bigtiff?
>
> Thank you for discussing this issue.
>
> Andreas
>
>