python's simplekml doesn't output "Alias" tag

Question

I'm writing a simple script using simplekml 1.3.5 (it's a Python liblary for generating KML) for climate data visualization.

import simplekml

kml_filename ='sample.kml'

kml = simplekml.Kml(open=1)
model = kml.newmodel(name="test_model")
model.altitudemode = simplekml.AltitudeMode.absolute
model.location.altitude = 500
model.location.latitude = 36.939055000000025
model.location.longitude = 140.037
model.orientation.heading = 90
model.orientation.tilt = 0
model.orientation.roll = 0
model.scale.x = 1000
model.scale.y = 1000
model.scale.z = 1000
model.link.href = "images/canvas.dae"
model.resourcemap.newalias(targethref="instance.png", sourcehref="mapping.png") 
kml.save(kml_filename)

this code generates following KML.

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2">
    <Document id="1672">
        <open>1</open>
        <Placemark id="1674">
            <name>test_model</name>
            <Model id="1673">
                <altitudeMode>absolute</altitudeMode>
                <Location>
                    <longitude>140.037</longitude>
                    <latitude>36.939055000000025</latitude>
                    <altitude>500</altitude>
                </Location>
                <Orientation>
                    <heading>90</heading>
                    <tilt>0</tilt>
                    <roll>0</roll>
                </Orientation>
                <Scale>
                    <x>1000</x>
                    <y>1000</y>
                    <z>1000</z>
                </Scale>
                <Link id="1678">
                    <href>images/canvas.dae</href>
                </Link>
                <ResourceMap>
                    <targetHref>instance.png</targetHref>
                    <sourceHref>mapping.png</sourceHref>
                </ResourceMap>
            </Model>
        </Placemark>
    </Document>
</kml>

It looks almost good. But Alias tag was not output in ResourceMap tag. I expected following output.

                <ResourceMap>
                    <Alias>
                    <targetHref>instance.png</targetHref>
                    <sourceHref>mapping.png</sourceHref>
                    </Alias>
                </ResourceMap>

The google earth didn't display the texture without this tag. (And add the tag manually, can display it.)

How I can output the tag in the KML using simplekml?

Answer 1

I think this is a ResourceMap class issue on the design poliy of the library.

import simplekml

rc = ResourceMap()
rc.newalias(targethref="foo", sourcehref="bar")
print(rc)

This code output following.

<targetHref>foo</targetHref><sourceHref>bar</sourceHref>

I hacked once by subclassing, but outer Model class checks the type and reject subclass. So I resolved with an adhoc hack to Alias class instead of ResourceMap.

class AliasModded(simplekml.Alias):
    def __init__(self, targethref=None, sourcehref=None):
        super(AliasModded, self).__init__(targethref, sourcehref)

    def __str__(self):
        return "<Alias>{}</Alias>".format(super(AliasModded, self).__str__())

and use this.

    tp_model.resourcemap.aliases.append(AliasModded(targethref="instance.png", sourcehref="mapping.png"))

This code output as expected. Thanks.