[gdal-dev] Optimisation of ECW files

Yves Jacolin yjacolin at free.fr
Tue Nov 8 05:40:33 EST 2011


I have an issue with one of my project which need some frequent update and I 
need some advice.

We have a dataset of small ECW files (5 300 files from 30 to 300 ko). This is 
not the way I want to manage my data to get good performance with MapServer. 
Too much file, too smal.

All this tiles don't form a regular single tile. I mean some part are hole.

Here is my issues after merging all the tiles:
* we lose extent in the final ECW file
* 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.

Any hints, advices?


Yves Jacolin


More information about the gdal-dev mailing list