[Qgis-user] Raster Layer Symbology Problem
Martin Bittens
martin.bittens at gmx.de
Fri Mar 12 03:30:02 PST 2021
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/
> <https://www.ecodiv.earth/post/legend-for-continuous-raster-in-qgis-composer/>
> image.png
>
> -Bas
>
> On Wed, Mar 10, 2021 at 2:34 PM Martin Bittens <martin.bittens at gmx.de
> <mailto: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
>> <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
>> <http://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
>> <http://gis.stackexchange.com/questions/388154/how-to-get-back-discrete-raster-legend-symbols-in-qgis-3-16>
>> twitter.com/ThomasG77/status/1365255399927140355
>> <http://twitter.com/ThomasG77/status/1365255399927140355>
>>
>>
>> On Tue, Mar 9, 2021 at 7:54 AM Bernd Vogelgesang
>> <bernd.vogelgesang at gmx.de <mailto: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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