[Qgis-user] Raster Layer Symbology Problem

[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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