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 <[email protected] >: > 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 > > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user >
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