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When I georeference a map of vegetationtyps (about 20 colours, each representing a certain vegetation) the quality of the georeferenced map is really bad and the some colours has changed (e.g. black becomes white), which makes it almost impossible to recognise the the certain types.

I did the "usuale" procedure: transformation type: linear, method: nearest neighbor. As source I tried jpeg & tiff, same bad result

Any suggestions how to improve the quality of the map and the originality of the map?

Thanks!

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Have your raster files paletted colours or rgb/rgba? I think rgba works better for reprojecting. –  Andre Joost Apr 29 '13 at 8:48
    
I don't know about QGIS, but ArcMap often defaults to a "standard deviations" stretched colour ramp when you add a newly georeferenced image. This often distorts the colours, although your example sounds pretty extreme. The solution in ArcMap is to set the 'stretch type' from Standard deviations to None. Perhaps the same applies in QGIS? –  JamesS Apr 29 '13 at 11:07
    
Thanks a lot for your response, but i does not work. However I just got the shape, so problem avoided. –  user16032 Apr 29 '13 at 16:04
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