QGIS does not display raster maps from a GRASS mapset

[qgib]

Author Name: Pedro Venâncio (Pedro Venâncio)
Original Redmine Issue: 20978
Affected QGIS version: 3.7(master)
Redmine category:grass

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Raster layers in GRASS mapsets are not rendered by QGIS 3.4.3 and master.

But, at least for some raster data types, just opening the layer properties and doing 'Ok', QGIS assumes a default color ramp and the raster shows up (see the attached gif).

So, it seems that QGIS 3.x is not interpreting GRASS color tables by default.

Using QGIS Value Tool plugin, the raster values are displayed correctly, even without the raster being rendered in canvas.

Veronica Andreo had tested in Linux. Her report is here: http://osgeo-org.1560.x6.nabble.com/QGIS-does-not-display-raster-maps-from-a-GRASS-mapset-td5390774.html

In QGIS 2.18.27, raster layers from GRASS Mapsets work without problems.

I don't know if this behaviour is somehow related, but using GRASS algorithms from QGIS Processing, when the outputs are rasters, the error message 6 from gdal is showed:

ERROR 6: SetColorTable() only supported for Byte or UInt16 bands in TIFF format.

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• QGIS_GRASS_Color_Table.gif (Pedro Venâncio)

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• regression was changed from 0 to 1

[qgib]

Author Name: Alexander Bruy (@alexbruy)

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As I understand, ERROR 6 comes from GDAL and caused by limitations of the TIFF format. If GRASS produces rasters with Float data type, then GDAL can't apply color map to them during confersion. Confirmed by Markus Neteler here https://gis.stackexchange.com/a/102605.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• status_id was changed from Open to Feedback

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Still true on master. On 3.* it fails to render the rasters even when gdal is used is the same as in 2.18 (where there is no issue).

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• version was changed from 3.4.3 to 3.7(master)
• status_id was changed from Feedback to Open

[nyalldawson]

I can't reproduce this, using a range of grass floating point rasters with color maps set. Is it still reproducible in recent QGIS?

Can someone provide step-by-step process to reproduce?

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[github-actions]

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