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. > * 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. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [email protected] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Software Developer _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
