Hello, Le mardi 8 novembre 2011 20:49:33, Frank Warmerdam a écrit : > On Tue, Nov 8, 2011 at 2:40 AM, Yves Jacolin <[email protected]> wrote: > > Here is my issues after merging all the tiles: > > * we lose extent in the final ECW file > > Yves, > > You don't mention how you are merging the files, but generally speaking > GDAL should be able to capture the extents and coordinate system when > writing to ECW. ECW coordinate system handling can be somewhat flaky > and it is possible that if the coordinate system mapping fails even the > extents are not written (or read) though I'm not sure about that. You may > need to pick a specific ECW coordinate system and specify it with > creation options if this is the source of the issue.
I used gdal_merge.py from a vrt file. I will test to assign a ECW coordinate system. > > * we have some black background which is not what expected > > * we need to update this final tiles frequently, and so we need fast > > process :) > > > > ECW format doesn't manage nodata so do it mean that I can't have > > alphaband and so I have no solution to get another background color > > (white or transparent)? > > > > Does exist some flag to save extent in the final ECW ? > > > > Have you some advice in order to get what I want (alphaband, good > > perfomance)? I can change file format if needed. We though to use TIFF > > files with a merge of some of them to get bigger tiles. We can either > > merge all the tiles, and then merge new tile with this final files or > > create tileindex for the bigger tiles. > > In theory you could maintain a separate alpha/mask file and associate > it using a wrapping VRT file around the ECW and alpha band. But this > is a somewhat complicated approach and it may also result in ECW > reads being done in chunks for MapServer which could substantially > impact performance. > > Also, in general, ECW is not updatable-in-place, so I don't see how > it could be suitable as a format for frequent updates. You basically > would need to regenerate it from the source tiles for each update. ok it was my conclusion also but I was not sure. Thanks, Y. -- Yves Jacolin _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
