Thank you Matthias and Mathieu for your for the messages! I hope and plan to 
obtain some valuable and usable outcome.
In fact, I don't know SNAP very well but band math + virtual raster bands could 
be an inspiration for some aspects.

Kind regards,
Francesco

________________________________
Da: Mathieu Pellerin <nirvn.a...@gmail.com>
Inviato: martedì 13 aprile 2021 16:06
A: Matthias Kuhn <matth...@opengis.ch>
Cc: Francesco Bursi <francesco.bu...@hotmail.it>; qgis-developer 
<qgis-developer@lists.osgeo.org>; Alister Hood <alister.h...@gmail.com>
Oggetto: Re: [QGIS-Developer] R: GSoC 2021 QGIS On-the-fly Raster Calculator 
proposal draft review and feedback

Big interest on my side too (and I'm sure countless more).

I always thought ESA's SNAP had a winning formula with their virtual raster 
bands, glad we can make any move in that direction.

Math

On Tue, Apr 13, 2021, 20:57 Matthias Kuhn 
<matth...@opengis.ch<mailto:matth...@opengis.ch>> wrote:
Hi Francesco,

This is a great initiative, thank you for taking on this.
I have just recently had a project where this would have been of great value. 
I'm very much looking forward to this work.

Welcome on QGIS board and enjoy your GSoC.

Matthias

On Tue, Apr 13, 2021 at 3:41 PM Francesco Bursi 
<francesco.bu...@hotmail.it<mailto:francesco.bu...@hotmail.it>> wrote:
Hi Alister,

Thank you for the feedback.
Well, I imagine the new feature with some properties of the existing Raster 
Calculator but not exactly the same, e.g It won't be possible to set layer 
extent / output CRS, because this would be already pre-defined by the layer on 
which the renderer is applied, in the basic mockup you should not see these 2 
field. The same can be said for choosing other layer. It should work like 
contours/hillshade renderer, where you can style only the layer you have 
currently selected but you can choose the band.
Besides, I think that the existing Raster Calculator in the processing toolbox 
(as well as the Gdal Raster Calculator) allows the creation of a temporary 
file, enable the addition of a layer to the project that you can style, but 
maybe here I misunderstood what you meant.
One of the advantage of the on-the-fly (styling) is to  avoid the need to 
create derived raster files and layers.

Let me know if I misunderstood something and thank you for the message.

Kind Regards,

Francesco Bursi

________________________________
Da: QGIS-Developer 
<qgis-developer-boun...@lists.osgeo.org<mailto:qgis-developer-boun...@lists.osgeo.org>>
 per conto di Alister Hood 
<alister.h...@gmail.com<mailto:alister.h...@gmail.com>>
Inviato: martedì 13 aprile 2021 14:10
A: qgis-developer@lists.osgeo.org<mailto:qgis-developer@lists.osgeo.org> 
<qgis-developer@lists.osgeo.org<mailto:qgis-developer@lists.osgeo.org>>
Oggetto: Re: [QGIS-Developer] GSoC 2021 QGIS On-the-fly Raster Calculator 
proposal draft review and feedback

Hi,
This functionality would be great, but as a user, I can't help thinking the 
proposal is to implement it in the wrong way.

If implemented as a renderer, as described, you could conceivably use an 
expression that uses other layers but not the layer you are supposedly 
rendering.  What is displayed would not correspond in any way to the actual 
layer... Bizarre.

Would it not be possible to instead implement a "virtual raster" *provider*?  
Add a checkbox in the raster calculator labelled "create as virtual raster".  
Create a new layer that can be styled using the existing renderers and behaves 
in every way like a non-virtual layer - e.g. the right values would be shown 
using the identify tool and the "value tool" plugin, and you could use the 
layer as an input for other processing tools.

Regards, and best wishes with the proposal,
Alister

Date: Mon, 12 Apr 2021 12:20:53 +0000
From: Francesco Bursi 
<francesco.bu...@hotmail.it<mailto:francesco.bu...@hotmail.it>>
To: qgis-developer 
<qgis-developer@lists.osgeo.org<mailto:qgis-developer@lists.osgeo.org>>
Subject: [QGIS-Developer] GSoC 2021 QGIS On-the-fly Raster Calculator
        proposal draft review and feedback
Message-ID:
        
<vi1p190mb038187bb910511b3b6b8b44280...@vi1p190mb0381.eurp190.prod.outlook.com<mailto:vi1p190mb038187bb910511b3b6b8b44280...@vi1p190mb0381.eurp190.prod.outlook.com>>

Content-Type: text/plain; charset="windows-1252"

Hello QGIS Dev,


I?m Francesco Bursi, an M.Sc. civil engineer from Italy currently enrolled in a 
Master of Advanced Studies (Level 8 EQF) in giscience and geoinformatics at the 
University of Padua.

I?m really interested in the QGIS (possible) new rendering feature that 
involves raster calculator capabilities, I've already discussed the project 
with mentors Martin Tobias and Peter Petrik and possible co-mentor Roberto 
Marzocchi,  they gave me a lot of feedback and advice for the project.
I would like to share my proposal with you before the final submission. Don't 
hesitate to give me feedback and ask me question/clarification or point me out 
what's missing.


proposal 
2021<https://docs.google.com/document/d/1u8L_L1IJjGCZ3d8Vq8duxHbsHZeyzwqOe3tXa1JcKbs/edit?usp=sharing>


I'm open to advice, remarks and criticism in order to improve.

I am looking forward to a feedback, thank you for your time.


Best regards,

Francesco Bursi
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