[Qgis-user] Symbolizing a discrete or a boolean raster (Stéphane Henriod)
Stéphane Henriod
s at henriod.info
Wed Jan 11 06:55:42 PST 2017
Thanks for checking, that's what I realized as well!
Do you know if there is still a chance to include it for 3.0 or is it too
late already?
Cheers
Stéphane
Le mercredi 11 janvier 2017, DelazJ <delazj at gmail.com> a écrit :
> Hi Stéphane,
>
> I gave it a look and I'm sorry I was wrong. There have been some work on
> the raster classification but it was rather about color and extent
> management. See https://github.com/qgis/QGIS/pulls?utf8=%E2%9C%93&q=is%
> 3Apr%20discrete%20is%3Aclosed%20 or https://github.com/qgis/QGIS/
> pulls?utf8=%E2%9C%93&q=is%3Apr%20pseudocolor%20is%3Aclosed%20 but testing
> upcoming 3.0 shows that nothing has changed in the area you are interested
> in.
>
> Harrissou
>
> 2017-01-11 4:37 GMT+01:00 Stéphane Henriod <s at henriod.info
> <javascript:_e(%7B%7D,'cvml','s at henriod.info');>>:
>
>> Hi Harrissou
>>
>> is there any description / documentation of the work that has been done
>> on this (feature description, etc.)? If yes, I'd like to have a look and
>> maybe
>>
>> Thanks a lot!
>>
>> Stéphane
>>
>>
>> Le mardi 10 janvier 2017, DelazJ <delazj at gmail.com
>> <javascript:_e(%7B%7D,'cvml','delazj at gmail.com');>> a écrit :
>>
>>> Hi Stéphane,
>>>
>>> 2017-01-10 4:02 GMT+01:00 Stéphane Henriod <s at henriod.info>:
>>>
>>>> Hi Chris
>>>> this is very nice! I indeed didn't know this trick and will certainly
>>>> use it again in the future!
>>>>
>>>> However... :-)
>>>>
>>>> I am currently teaching QGIS to beginners and this for sure is not an
>>>> appropriate method for them (especially in the case you have to generate
>>>> the symbology file through a script)!
>>>>
>>>> Since the user can style continuous rasters with some
>>>> "button-clicking", I believe the same option should be available for
>>>> discrete rasters as well.
>>>>
>>>> I am thus wondering if anyone else than me sees it as a priority for
>>>> QGIS? If yes, how to motivate the developers to take it for the next
>>>> release and / or how much would such a development cost? (I unfortunately
>>>> don't have the competences to do it myself)
>>>>
>>>> There have been some work done in the raster properties dialog in the
>>> upcoming 3.0. I don't know if your concern was covered though.
>>> If you want, you can move the question to the developer's list
>>> <http://qgis.org/en/site/getinvolved/mailinglists.html#qgis-developers-list>
>>> and discuss whether/how this can be implemented (and its requirements).
>>>
>>> Regards,
>>> Harrissou
>>>
>>> Thanks again and cheers!
>>>>
>>>> Stéphane
>>>>
>>>>
>>>> Le mardi 10 janvier 2017, Chris House <housec01 at gmail.com> a écrit :
>>>>
>>>>> Hi Stéphane,
>>>>>
>>>>> I don't know if this is what you are looking for or not but I have a
>>>>> method of classifying rasters by color based on a set (standard) colors. I
>>>>> created a spreadsheet that has several required columns, value, red, green,
>>>>> blue...and you can have an optional field for a display value. So say
>>>>> value 1 is water you can use that last column to name that value so that in
>>>>> the QGIS layer tree and in legend it says Water instead of value 1.
>>>>>
>>>>> save the spreadsheet as a csv and change the extension to .txt instead
>>>>> of .csv.
>>>>>
>>>>> I then go into the symbology section of the raster choose singleband
>>>>> pseudocolor. Use the folder to browse to your text file and click add.
>>>>> There is a format for this text file. It is below. If you need me to
>>>>> email it I will do that in direct email.
>>>>>
>>>>> # QGIS Generated Color Map Export File
>>>>> INTERPOLATION:EXACT
>>>>> -9999,0,0,0,255,NoData
>>>>> 0,176,176,176,255,Non-Forested
>>>>> 15,234,255,191,255,10 <= CC < 20
>>>>> 25,187,230,149,255,20 <= CC < 30
>>>>> 35,140,201,109,255,30 <= CC < 40
>>>>> 45,98,176,74,255,40 <= CC < 50
>>>>> 55,59,153,43,255,50 <= CC < 60
>>>>> 65,0,128,0,255,60 <= CC < 70
>>>>> 75,15,92,11,255,70 <= CC < 80
>>>>> 85,17,61,12,255,80 <= CC < 90
>>>>> 95,16,36,12,255,90 <= CC <= 100
>>>>>
>>>>> In my example if I don't assign a value it gets ignored by QGIS. If
>>>>> you are wondering how to assign unique colors to say 200 unique
>>>>> values...just script it. I have done this and as long as you have the
>>>>> number of unique values you want and to make them unique in the script it
>>>>> works.
>>>>>
>>>>> I hope this helps. I know it isn't a "button" but to be honest I like
>>>>> this better. If you already knew this...well then maybe it will help
>>>>> someone out in the future.
>>>>>
>>>>> --Chris
>>>>>
>>>>> On Mon, Jan 9, 2017 at 3:00 PM, <qgis-user-request at lists.osgeo.org>
>>>>> wrote:
>>>>>
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>>>>>> Today's Topics:
>>>>>>
>>>>>> 1. Re: Symbolizing a discrete or a boolean raster (Stéphane
>>>>>> Henriod)
>>>>>>
>>>>>>
>>>>>> ------------------------------------------------------------
>>>>>> ----------
>>>>>>
>>>>>> Message: 1
>>>>>> Date: Mon, 9 Jan 2017 23:07:36 +0600
>>>>>> From: Stéphane Henriod <s at henriod.info>
>>>>>> To: Enrico Fiore <enricofiore at libero.it>
>>>>>> Cc: qgis-user <qgis-user at lists.osgeo.org>
>>>>>> Subject: Re: [Qgis-user] Symbolizing a discrete or a boolean raster
>>>>>> Message-ID:
>>>>>> <CAK6pVBXURm_e7dRP+8SP9amPUUX0+Cn3GVxLPNjOHhno85o2rA at mail.gm
>>>>>> ail.com>
>>>>>> Content-Type: text/plain; charset="utf-8"
>>>>>>
>>>>>> Hi
>>>>>>
>>>>>> thanks for following up!
>>>>>>
>>>>>> It actually does part of the job!
>>>>>>
>>>>>> Using *Color interpretation: Exact*, I can indeed input the exact
>>>>>> values I
>>>>>> want to display (1,5 and 10) and all other pixels are hidden.
>>>>>>
>>>>>> HOWEVER,
>>>>>>
>>>>>> this still feels like a workaround:
>>>>>>
>>>>>> - In the case of a discrete raster with many (> 50) unique values,
>>>>>> I do
>>>>>> not want to input all of them manually
>>>>>> - In some cases, I do not know in advance all the unique values of
>>>>>> my
>>>>>> raster
>>>>>> - If I click on *Classify*, QGIS will choose X values (based on the
>>>>>> number of classes and the classification method (continuous or
>>>>>> equal
>>>>>> interval)), which no longer match the "exact" values of my raster.
>>>>>> It
>>>>>> doesn't really make sense to classify a discrete rendering
>>>>>>
>>>>>> So I would say, we still need a render type "discrete raster" which
>>>>>> offers
>>>>>> the function to "retrieve all unique values" (and automatically apply
>>>>>> a
>>>>>> discrete color ramp)
>>>>>>
>>>>>> Attached a (fake) test dataset.
>>>>>>
>>>>>> Thanks and cheers
>>>>>>
>>>>>> Stéphane
>>>>>>
>>>>>>
>>>>>> Le lundi 9 janvier 2017, Enrico Fiore <enricofiore at libero.it> a
>>>>>> écrit :
>>>>>>
>>>>>> > Hi,
>>>>>> > Sorry I can't do test, but if you use exact in color interpolation
>>>>>> > parameter?
>>>>>> >
>>>>>> > Cheers
>>>>>> >
>>>>>> > Enrico
>>>>>>
>>>>>>
>>>>>> Le lundi 9 janvier 2017, Stéphane Henriod <s at henriod.info> a écrit :
>>>>>>
>>>>>> > 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
>>>>>> > <javascript:_e(%7B%7D,'cvml','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_r
>>>>>> >> aster/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>
>>>>>> >> Data: 09/01/2017 6.30
>>>>>> >> A: "qgis-user"<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/009t00
>>>>>> 000074000000/
>>>>>> >> 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-d
>>>>>> >> iscrete-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 <+49%20176%2028011050> (DE)
>>>>>> E s at henriod.info
>>>>>> W http://www.stat.kg
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>>>>>>
>>>>>
>>>>>
>>>>
>>>> --
>>>> 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 <+49%20176%2028011050> (DE)
>>>> E s at henriod.info
>>>> W http://www.stat.kg
>>>> W3W: nightfall.into.bucket
>>>> <https://map.what3words.com/nightfall.into.bucket> //
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>>>
>>>
>>
>> --
>> 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 <+49%20176%2028011050> (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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