[Qgis-developer] [Qgis-user] Raster Calculator and LN

[George Silva]

This looks like a bug.

Even thought I'm programming with the raster calculator, there are strong
tells that this is a bug. I tested this programming and using the inteface:
same results.

In the attachment there is the file I'm working with. I tried this simple
math:

* radiance.tif

(raster * 0.03705882) + 3.2

It's output is all NODATA.

I've tried:

raster + 1

It's output is NODATA.

raster * 0.5

It's output is NODATA.

If that's not a bug I'm not sure what it is. It looks like on 2.6 it was
fine. I'm working on this for two days, and unless I'm doing something
really really wrong, it think it's a bug.

Please, see the TIF imagery attached (zip).

All the formulae is simple and should work without issues.

George

On Tue, Mar 24, 2015 at 1:28 PM, Nicolas Cadieux <
nicolas.cadieux at archeotec.ca> wrote:

> Hi,
> Could it be that for your layer, 0 = null?  In that case, could this be
> the source of the problem?  Try changing the null value to test... Just an
> idea.
>
> Nicolas Cadieux M.Sc.
> Les Entreprises Archéotec inc.
> 8548, rue Saint-Denis Montréal H2P 2H2
> Téléphone: 514.381.5112  Fax: 514.381.4995
> www.archeotec.ca
> Le 2015-03-24 10:24, "george-silva [via OSGeo.org]" <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=5195208&i=0>> a écrit :
>
> Hello everyone,
>
> It seems that we have a bug on raster calculator. I tried searching the
> web for this, but here's the story:
>
> I'm developing a plugin that makes extensive use of the raster calculator.
> So far so good. I can enter my custom expressions and it seems to be
> working fine.
>
> However one of my formulas contains a LN (natural log). So, to test this
> properly I've created a raster all with 1 value. The LN for 1 is 0, so the
> whole raster should be zeroed.
>
> The raster calculator, even while programming or using the software, tells
> me that the expression is valid.
>
> That's not the case.
>
> Questions:
>
> 1) Is LN not implemented in the raster calculator? Is implemented? What is
> the syntax? Is it documented?
>
> 2) Workarounds?
>
> Is it a bug? I'm trying to look my redmine password so I can file a bug or
> contribute with documents for testing.
>
> Thanks
>
> George
>
> --
> George R. C. Silva
> SIGMA Consultoria
> ----------------------------
> http://www.consultoriasigma.com.br/
>
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-- 
George R. C. Silva
SIGMA Consultoria
----------------------------
http://www.consultoriasigma.com.br/
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