How to automatically stretch raster in QGIS? (ArcGIS DRA dynamic range adjustment analogue)

Question

I am looking for ArcGIS's dynamic range adjustment (DRA) analouge in QGIS for raster data sets. And I have found such button:

But I have to click it every time I move raster's extent.

There is any way to automate manual clicking the button?

Answer 1

Unfortunately, this feature is not available without some python scripting, but will be available in 3.0.

See https://github.com/qgis/QGIS-Documentation/issues/1583

@QGIS-feature-tracker QGIS-feature-tracker added this to the QGIS 3.0 milestone on Dec 16, 2016

Answer 2

Nice find by @RoVo! There is also an alternative.

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For QGIS 2.x

We could use a little bit of Python where each time the extent of the canvas changes, we connect the signal that is emitted to a function which triggers the button you mentioned.

So you could use something like the following in the Python Console:

from PyQt4.QtGui import QAction

def stretch_raster():
    try:
        layer = iface.activeLayer()
        if layer.type() == QgsMapLayer.RasterLayer:
            iface.mainWindow().findChild( QAction, 'mActionLocalCumulativeCutStretch' ).trigger()
    except AttributeError:
        pass

iface.mapCanvas().extentsChanged.connect(stretch_raster)

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Note that the button will only be triggered if a raster layer is selected from the Layers Panel. When you want to disconnect the signal from the function, you can use:

iface.mapCanvas().extentsChanged.disconnect(stretch_raster)