[Qgis-developer] min/max for rasters

[Radim Blazek]

On Fri, Dec 13, 2013 at 9:55 AM, Paolo Cavallini <cavallini at faunalia.it> wrote:
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> Hi all.
> The default for raster rendering is to cut values at 2-98%. This is
> inappropriate in many cases, and confusing for users. Is that OK if I
> change the default to min/max?

Min/max is inappropriate in many other cases. It is quite common to
get data with few outliers. The result in such cases with min/max is
black rectangle which is very frustrating and that was the case with
1.8.

I believe that it is better to get inappropriately rendered picture
than black rectangle. I understand however that it may be problem that
user does not notice that the cut was applied.

If we find 2-98% as bad as bad min/max we should invent something
better, not just switch from one bad solution to another one. We can
discuss for example the range (2-98%,1-99%,0.1-99.9%...) and different
situations (data types, number of bands).

Can you describe some examples where 2-98% is a problem (data type,
number of bands, map content, features/phenomena represented by those
2+2%,...) so that we can think about it better?

Radim

> All the best.
> - --
> Paolo Cavallini - www.faunalia.eu
> QGIS & PostGIS courses: http://www.faunalia.eu/training.html
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