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I'm new on QGIS and PyQGIS. I'm trying to create a plugin which aims to apply a style on a vector layer (generated from a csv file) and then save the map as a png file.

The style I apply on the vector layer is a heatmap style. The problem is that I don't have a legend for the heatmap.. . At least I would like to have the colors and the percentage of the different levels.

Do you have any idea of how I could do that? Or is it even possible?

I'm not using the heatmap plugin, only applying a heatmap style from a .qml file.

I searched a lot and I couldn't find anything helpful about that... any help would be great.

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You may get access to the default ramp colors in this way:

defStyle = QgsStyleV2().defaultStyle()
defaultColorRampNames = defStyle.colorRampNames()
print defaultColorRampNames

# The print command returns this list:
# [u'Blues', u'BrBG', u'BuGn', u'BuPu', u'GnBu', u'Greens', u'Greys', u'Inferno', u'Magma', u'OrRd', u'Oranges', u'PRGn', u'PiYG', u'Plasma', u'PuBu', u'PuBuGn', u'PuOr', u'PuRd', u'Purples', u'RdBu', u'RdGy', u'RdPu', u'RdYlBu', u'RdYlGn', u'Reds', u'Spectral', u'Viridis', u'YlGn', u'YlGnBu', u'YlOrBr', u'YlOrRd']

Then, you may set the ramp by specifying the index of the ramp from the list printed in the previous code (for example, 0 is the index for the 'Blues' ramp):

ramp = defStyle.colorRamp(defaultColorRampNames[0]) # 0 is the index for the 'Blues' ramp

or by directly typing the color ramp's name:

ramp = defStyle.colorRamp('Blues')

With these premises, you may use this sample code:

layer = iface.activeLayer() # load the layer as you want

defStyle = QgsStyleV2().defaultStyle()
defaultColorRampNames = defStyle.colorRampNames()

renderer = QgsHeatmapRenderer()
renderer.setRadius(5) # change the radius value as you want
renderer.setMaximumValue(0) # set 0 for automatically calculating it
ramp = defStyle.colorRamp('Blues')
renderer.setColorRamp(ramp)
renderer.setWeightExpression('my_field') # set the field name here
layer.setRendererV2(renderer)
layer.triggerRepaint()

for creating a Heatmap renderer (of blues):

enter image description here

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