Question about white background in ECW files

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Question about white background in ECW files
By Michał in ERDAS Software Forum

Hello friends

I had a problem with white background of mosaic and I solve it. Now I have a problem with white background of each ECW files (wchich mosaic is build).When i scroll up- I don't see a white background because I'm in mosaic but when I Scroll down near by border is big white background.

Anybody know how to delete or make invisible whie background in ECW file?

I make a convert from GeoTiff to ECW and there is nothing about "Ignores Values" ( like is in Mosaic).

 

Thank You from the mountain

M.B

 

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Re: Question about white background in ECW files
By Timo Ikola in ERDAS Software Forum

White background in ecw has been the desigend feature for ages. The point is that ecw compression makes near zero values to black background (actual zeros) that is visible as a black edges. Then depending on software used this is then worked around by adding black or white backgrounds depending which one current software uses. ArcGIS for example uses white background and in it 255 is optimal pixel value for background while Imagine uses black and zero is better for that.

All solutions have been workarounds having some pros and cons until Erdas version 2010 which introduced ecw transparency mask. That is available in Imagine just in ecw export side - not in direct write. So in practise really solve this issue you need to go latest Erdas version and apply this transparency mask in your ecw writing processes. With that you have a real change to make it work correctly in all tools without different color edges. If you try with old versions be prepared on black or white edges - depending on case and tools used.

 

timo

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