[Qgis-user] Symbolizing a discrete or a boolean raster

[Stéphane Henriod]

Hi

unfortunately this is doing quite something different!

If I have a raster with 10 Landcover classes (1,2,3,4,5,6,7,8,9,10) and I
want to display only 1,5 and 10, using *Discrete *(1: red, 5: yellow, 10:
blue) the following will happen:

All pixels between 1 and 4 will be red
All pixels between 5 and 9 will be yellow
All pixels with 10 will be blue

In this sense, the pixels are indeed not interpolated, but this still is
not the behavior I am expecting when styling discrete rasters.

A "style discrete raster" function should offer the following:

   - Automatically recover all unique values from the raster
   - Only display the pixels to which the user has explicitly assigned a
   color

But thanks for your hint, this can be helpful in other cases!

Cheers

Stéphane


Le lundi 9 janvier 2017, Enrico Fiore <enricofiore at libero.it> a écrit :

> Hi,
> I think that the solution is in the QGIS documentation, that you can read
> here: http://docs.qgis.org/2.14/en/docs/user_manual/working_with_
> raster/raster_properties.html#band-rendering
> you have to use *Singleband pseudocolor *and set color interpolation to
> Discrete.
>
> Enrico
>
>
> ----Messaggio originale----
> Da: "Stéphane Henriod" <s at henriod.info
> <javascript:_e(%7B%7D,'cvml','s at henriod.info');>>
> Data: 09/01/2017 6.30
> A: "qgis-user"<qgis-user at lists.osgeo.org
> <javascript:_e(%7B%7D,'cvml','qgis-user at lists.osgeo.org');>>
> Ogg: [Qgis-user] Symbolizing a discrete or a boolean raster
>
> Dear all
>
> As much as I love QGIS and use it in my everyday life, there is one
> feature that I find particularly annoying: the styling of discrete rasters.
>
> Basically, if I have a raster layer consisting of discrete landcover
> values (1: water, 2: forest, 3: built-up), it seems that there is no easy
> way to style it. QGIS will assume that the data is continuous and basically
> interpolate the color between each value, which leads to the following
> issues:
>
> Let's say I want to display only water and built-up (values 1 and 3),
> water in blue and built-up in grey. QGIS will still display the forests,
> using a color somewhere "between" blue and grey. My only left option is to
> process the raster to actually replace all the 2 with NoData, which is
> highly unpractical...
>
> Same if I have a boolean raster (only 0 and 1 values). QGIS will by
> default make a color ramp from 0 to 0.9999.
>
> Also, the whole rather feels like a work-around for a missing feature.
>
> I dream of a feature similar to this one from ArcGIS: http://resources.
> arcgis.com/en/help/main/10.1/index.html#/representing_
> unique_categories_such_as_land_use/009t00000074000000/ where all unique
> values are styled independently and where I can easily skip the values I
> don't want to see on my map.
>
> I asked a question here:
> http://gis.stackexchange.com/questions/194116/qgis-style-a-discrete-raster
>
> and opened a ticket here:
> http://hub.qgis.org/issues/14845
>
> But none has gotten lots of attention yet... Am I the only one to be
> annoyed by this? If no, please raise your hand and let's try to get some
> momentum and see how to push this feature forward!
>
> Thanks a lot in advance!
>
> Cheers
>
> Stéphane
>
>
> --
> Stéphane Henriod
> CIM-Expert for GIS and Green Economy Statistics
>
> Национальный статистический комитет Кыргызской Республики
> Кыргыз Республикасынын Улуттук статистика комитети
> National Statistical Committee of the Kyrgyz Republic
>
> 374 Фрунзе ул. / Frunze str.
> 720033 Бишкек / Bishkek
>
> T   +996 778 46 99 02 (KG)
> T   +49 176 280 11 050 (DE)
> E    s at henriod.info <javascript:_e(%7B%7D,'cvml','s at henriod.info');>
> W   http://www.stat.kg
> W3W: nightfall.into.bucket
> <https://map.what3words.com/nightfall.into.bucket>  //  запас.союз.дружный
> <https://map.what3words.com/запас.союз.дружный>
>
>
>
>

-- 
Stéphane Henriod
CIM-Expert for GIS and Green Economy Statistics

Национальный статистический комитет Кыргызской Республики
Кыргыз Республикасынын Улуттук статистика комитети
National Statistical Committee of the Kyrgyz Republic

374 Фрунзе ул. / Frunze str.
720033 Бишкек / Bishkek

T   +996 778 46 99 02 (KG)
T   +49 176 280 11 050 (DE)
E    s at henriod.info
W   http://www.stat.kg
W3W: nightfall.into.bucket
<https://map.what3words.com/nightfall.into.bucket>  //  запас.союз.дружный
<https://map.what3words.com/запас.союз.дружный>
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