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I have two ecw-files. Both have no rectangular shape and overlap each other. When I combine both with a RasterMosaicker. The combined ecw-file has black, I think no-data, areas at the section between them. Can I make these area's transparent?

 

I thought of two options, but I don't know how to use them correct:

 

a Rastermosaicker option Nodata Overwrites Data: yes or no

 

b Composite using Alpha Band: yes or no

 

a: I tried both yes and no but both times the result was a black area

 

b: I tried to set it on yes but then the script fails: the log file reads: "All input files must have exactly one alpha band selected".

 

What do I do wrong? What do I have to do?
Hi Jorg,

 

 

you can try to use the RasterBandNoDataRemover bevor the RasterMosaiker. Hopefully that helps,

 

best regards,

 

Stefan
Thx. That seems easy.

 

I tried it, but it look like these areas are not "no-data" areas, because the resultin image is still with this "black area".
Hi Jorg,

 

 

Did you have a look at this excellent answer of Mark?

 

Hope this helps
I have found with ECWs that this black area is not pure black but a range of very similar shades.  ECWs seems to degrade pure colours during compression (eg. white RGB 255;255;255 compressed as 254;255;249).  Take a sample of the RGB values in the black area and see if this is the case.  I have had some success in 'cleaning' these 'dirty' black or white colours to a pure black and then using the RasterBandNoDataSetter.  I've got a custom transformer I can share if I can figure out how to get it to you Jorg.

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