partial fix for SAGA RGB composite tool

[gioman]

Description

The SAGA "RGB Composite" has wrong parameters names. Anyway this is not a complete fix:

this tool MUST output an "image", explanation here:

https://gis.stackexchange.com/a/301146

and this is the reason the tool output is generated as a special case here:

https://github.com/qgis/QGIS/blob/master/python/plugins/processing/algs/saga/SagaAlgorithm.py#L324

but the problem (unresolved by this patch) is that now SAGA outputs only in its native format, while this export operations MUST generate a TIFF (for example), otherwise the output (now generated because of the correct parameters names) will not show the expected values/colors (in fact it won't even be a RGB raster).

Checklist

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[luipir]

but the problem (unresolved by this patch) is that now SAGA outputs only in its native format, while this export operations MUST generate a TIFF (for example), otherwise the output (now generated because of the correct parameters names) will not show the expected values/colors (in fact it won't even be a RGB raster).

It's a decision by design to avoid implicit transformation and leave the original format to the backend that are not designed to produce a different format. This can be solved cascading the algorithm to a converter (if available).

[luipir]

@gioman as usual, please add a test ;)

[gioman]

It's a decision by desing to avoid implicit transformation and leave the original format to the backend that are not designed to produce a different format. This can be solved cascading the algorithm to a converter (if available).

@luipir I'm aware that now SAGA outputs only in its native format. What I wanted to point in this PR is that in this specific case this strategy does not work. With the now fixed parameters names the tool will generate an output but this is wrong (is not the expected RGB raster). So this specific tool that is already handled as a special case must be tweaked to work.

In the SAGA command line here

https://github.com/qgis/QGIS/blob/master/python/plugins/processing/algs/saga/SagaAlgorithm.py#L324

"filename" must be defined as (example) a TIF output.

I tried to add a + '.tif' here

https://github.com/qgis/QGIS/blob/master/python/plugins/processing/algs/saga/SagaAlgorithm.py#L321

but it still generate a SAGA raster.

[gioman]

@gioman as usual, please add a test ;)

@luipir waiting for a live workshop in Coruña ;)

[stale]

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[stale]

While we hate to see this happen, this PR has been automatically closed because it has not had any activity in the last 21 days. If this pull request should be reconsidered, please follow the guidelines in the previous comment and reopen this pull request. Or, if you have any further questions, just ask! We love to help, and if there's anything the QGIS project can do to help push this PR forward please let us know how we can assist.

[luipir]

@nyalldawson ok to merge also without test? for me it's ok... waiting for a processing test crash course ;)

[nyalldawson]

@luipir my understanding is that this is only a partial fix and needs follow up work to fix the actual issue. @gioman can you confirm?

[luipir]

well, seems that at least this PR is necessary to generate correct values... other aspect is that these values are in a manageable format... btw wait for @gioman opinion

[nyalldawson]

Fix inbound

[nyalldawson]

See #8597

[gioman]

@gioman can you confirm?

@nyalldawson sorry fot late reply, yes I confirm.

[ThirstyGeo]

This issue is still present in QGIS version 3.4.3-Madeira - should the fix have rolled out in the last QGIS update?