[gdal-dev] Re: Flashy colors in a pyramid

Christian Müller christian.mueller at nvoe.at
Wed Aug 19 07:04:03 EDT 2009

Hi, Christian speaking, I wrote the gdal_retile.py utility. 

Could you try to run a gdal_merge.py on the highest pyramid level containing 
this strange area. What is the result.?  I want to know if the problem is 
gdal_retile.py or geoserver. 


acangi writes: 

> Hello list, 
> I created a pyramid of aerial photos using gdal_retile.py and now see there
> are strange zones in the pyramid. I'm trying to understand why I got this
> strange results and how I can fix it (Bombing the area to make sure it looks
> like what I have ?). Description :
> 1. The command I used was gdal_retile.py -targetDir pyramid/ -levels 12
> -pyramidOnly -v -s_srs /path/to/prjs/3812.prj -ps 10000 10000 -r bilinear
> -co "TILED=YES" -co "COMPRESS=LZW" -co "INTERLEAVE=PIXEL" -tileIndex
> orthocol -tileIndexField location /path/to/source/files/*.tif &
> 2. In the source files, I see nothing special. The tiles in this area look
> like the other ones.
> 3. On the first (generated) level of the pyramid, I see a small area (alias
> SMALL_SQUARE : 256m x 256m) in blue :
> http://n2.nabble.com/file/n3470903/BlueSquare.jpg 
> 4. On the next levels of the pyramid, a black rectangle 512m x 256m is now
> visible where SMALL_SQUARE was : 
> http://n2.nabble.com/file/n3470903/BlackRect.jpg  
> and the area corresponding to the first level tile containing SMALL_SQUARE
> (alias BIG_SQUARE : 10000m x 10000m) is in green : 
> http://n2.nabble.com/file/n3470903/GreenSquare.jpg 
> 5. I view the pyramid in geoserver, the tiles look like they are on disk,
> except at the first level, geoserver doesn't show me the full SMALL_SQUARE,
> only parts of it. In geoserver logs, I find nothing very interesting, it all
> looks the same whether or not I'm looking at BIG_SQUARE.
> 6. If I set OutputTransparentColor to #000000 (the background color),
> BIG_SQUARE is now invisible (in geoserver) 
> So, my questions are :
> Why did it happen ? I suppose it's just a random error...
> How can I fix it ? Is there any way other than rebuilding the whole pyramid
> ? 
> Any idea is welcome, 
> Alain
> -- 
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