[Qgis-user] Raster Layer Symbology Problem

Fri Mar 12 08:55:13 PST 2021

Martin,
The link that Alessandro provided was indeed the ability to revert back to
the previous discrete method. https://github.com/qgis/QGIS/pull/42193
As the pull request has a Backport 3.18 flag on it I assume that that means
that for the 3.18.1 release next week there should be the ability to turn
off continuous raster legend!
-Bas

On Fri, Mar 12, 2021 at 6:30 AM Martin Bittens <martin.bittens at gmx.de>
wrote:

> Hello Sebastian,
>
> thank you for your response. Yes indeed, for me the coloring style you
> showed would be an option. This style is what I get in GRASS GIS as well.
> But😁,
>
> what I would prefer in QGIS is this (as provided by QGIS 3.16.4 LTR):
>
>
> So I hope that in future QGIS versions, the user will have the choice
> between the different display options. As far as I understood the
> discussions in the links you sent there is something going on in order to
> add an option for selecting the new  or the old display style.
> Unfortunately, I am not an expert in that programming stuff and therefore I
> don't know how to apply what there is explained. I will wait and see what
> the next QGIS versions offer for displaying raster gradient legends. And I
> will keep the QGIS 3.16.4 LTR with special care not loosing the display
> style I showed above.
>
>
> Regards
>
>
> Martin
>
>
> Am 3/10/2021 um 5:54 PM schrieb Sebastian Gutwein:
>
> Martin,
> I agree with your assessment.
> I assume the assumption of the designers (thank you Nyall Dawson et al for
> all of your amazing work) was that if you were displaying a
> continuous raster you would want a continuous legend as well.
> As shown by your issue and in the links I shared with you the reality is
> that this doesn't fit all use cases.
> I am considering writing up a feature request to address those issues.
> Unless you want to?
> To help me understand your use case more would a legend that was
> continuous but had numerical values at each "break" work for you? An
> example of this is in this tutorial
> https://www.ecodiv.earth/post/legend-for-continuous-raster-in-qgis-composer/
> [image: image.png]
>
> -Bas
>
> On Wed, Mar 10, 2021 at 2:34 PM Martin Bittens <martin.bittens at gmx.de>
> wrote:
>
>> Sebastian, Bernd,
>>
>> thanks a lot for your response. I checked the links Sebastian sent. As
>> far as I could see displaying data in the legend as a continuum is a new
>> feature in QGIS 3.18 which replaced the previous method displaying data in
>> the legend as categories (as QGIS 3.16.4 is still doing - fortunately.
>> Otherwise it would be difficult producing maps in ongoing projects in a
>> consistent layout). And obviously there is no option available switching
>> between the old and the new display method. Personally I think it was not a
>> good decision giving up completely the categorical display in the legend.
>> In particular if you would work with multiple colors and a large range of
>> values, there is no way to allocate map colors to the corresponding values,
>> or vice versa.
>>
>> So, I hope that the next QGIS version will include an option which allows
>> selecting the method how to  display the data, as continuum or categorized.
>>
>>
>> Regards
>>
>> Martin
>>
>>
>> Am 3/9/2021 um 4:18 PM schrieb Sebastian Gutwein:
>>
>> Martin,
>> I think this may be the result of the new feature
>> https://qgis.org/en/site/forusers/visualchangelog318/#feature-gradient-ramp-based-legends
>> Which is exciting for me becasue that is how I would like to have my
>> continious data display. But it sounds like that is not what you are
>> interested in. I have not tried 3.18 myself so don't know if there is a
>> workaround.
>> It does look like there are some links to discussions in the comments of
>> this stack exchange question.
>> gis.stackexchange.com/questions/388843/qgis-3-18-override-raster-gradient-legends
>>
>> gis.stackexchange.com/questions/388154/how-to-get-back-discrete-raster-legend-symbols-in-qgis-3-16
>> twitter.com/ThomasG77/status/1365255399927140355
>>
>>
>> On Tue, Mar 9, 2021 at 7:54 AM Bernd Vogelgesang <
>> bernd.vogelgesang at gmx.de> wrote:
>>
>>> Without testing I would say it's a bug. Quite some bugs went into 3.18
>>> unnoticed and unfortunately, it's not  communicated on the landing page.
>>> Next regular point release will be in 10 days, but for urgent stuff, you
>>> should better use 3.16.
>>>
>>>
>>> On 09.03.21 13:32, Martin Bittens wrot:
>>> > Hello QGIS User List, i
>>> >
>>> > I already sent this message but it was not posted, so it is here again.
>>> > Hopefully it works now.
>>> >
>>> >
>>> > I am still struggling with the problem creating a legend for a raster
>>> > layer. Usually I am working with the following settings in order to
>>> > colorize a calculated raster layer (e.g. after applying v.surf.idw on a
>>> > point data set):
>>> >
>>> > - rendering type: singleband pseudocolor
>>> >
>>> > - interpolation: linear
>>> >
>>> > - mode: equal interval
>>> >
>>> >
>>> > In QGIS 3.18.0:
>>> >
>>> > Selecting an appropriate color ramp and applying a classification in,
>>> > e.g., 5 classes, I see in the "Layer Properties - Symbology" window the
>>> > 5 colored classes separately and the corresponding 5 values (in my case
>>> > temperatures) for each color coding. But in the "Layer Panel" the
>>> legend
>>> > shows the color coding as a continuum and only the first and last value
>>> > of the value range appears. The same thing happens in the layout
>>> manager
>>> > when I create a layout for printing which includes a legend.
>>> >
>>> > In QGIS 3.16.4 LTR and previous versions:
>>> >
>>> > Doing the same I get the 5 color classes separately and the
>>> > corresponding values for each of the 5 classes in the "Legend Panel"as
>>> > well as in the layout manger.
>>> >
>>> >
>>> > My question: Is this a bug in the new QGIS version or does QGIS 3.18
>>> not
>>> > provide this functionality anymore?
>>> >
>>> >
>>> > Thanks a lot for a comment.
>>> >
>>> >
>>> > Regards
>>> >
>>> >
>>> > Martin
>>> >
>>> >
>>> >
>>> > --
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