[Qgis-user] How to convert ECW using open source packages into something else?

[Enrique]

Summing up my experience with GTIF orthoimages, based on suggestions from
other users, if someone is interested in:

- GTIF with internal JPEG compression + internal pyramids/overviews also
with JPEG compression (see a. and b. commands below as examples).
- As you said, required GDAL compiled with ECW (FWTools on Windows, for
example).


GDAL commands:

a. Reading ECW and compressing to JPG (set your favourite quality, 80 is a
good choice for orthoimages; also CACHEMAX could be increased):

gdal_translate --config GDAL_CACHEMAX 1000 --config GDAL_PAM_ENABLED NO -of
GTIFF -co COMPRESS=JPEG -co JPEG_QUALITY=80 -co PHOTOMETRIC=YCBCR
"source_image.ecw" "target_image.tif"

b. Adding internal pyramids/overviews with JPG compression (select your
resampling method, I prefer average):

gdaladdo --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW
YCBCR --config INTERLEAVE_OVERVIEW PIXEL -r average "image.tif" 2 4 8 16 32
64 128


I'm using a batch script on Windows, useful to be applied to a set of
selected images on File explorer. I hope it's easy to write a script in
bash or python, if you are able to install ECW support on GNU/Linux.

Unfortunatly, a lot of public images are locked in ECW format (for example
our orthoimages at Spanish National Geographic Institute (IGN) [1
<http://www.ign.es/atom/dataset_feeds/_pnoaMA.es.xml>]), but I know they
are doing an effort to release them as GTIF, could be with internal JPEG.

Enrique.

[1 <http://www.ign.es/atom/dataset_feeds/_pnoaMA.es.xml>]
http://www.ign.es/atom/dataset_feeds/_pnoaMA.es.xml



2015-08-04 5:45 GMT+02:00 Simon Cropper <contact at simonchristophercropper.com
>:

> Hello,
>
> I have recently tried to get QGIS to work with ECW files.
>
> Despite several days of multiple
> installs/reinstalls/uninstalls/lib-upgrades/etc I have not managed to get
> ECW to be opened by QGIS. This is really frustrating as I am keen to use
> QGIS on an upcoming project.
>
> As an alternative, I would like to pose the following couple of
> questions...
>
> My first question is, what is a good alternative to ECW files for use on
> QGIS?
>
> The second question, how do I convert the ECW file into this format
> without using a propriety software package?
>
> --
> Cheers Simon
>
>
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> Qgis-user at lists.osgeo.org
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