Exporting data frame as PNG after adding Layer File using ArcPy in ArcMap

Question

My question relates to the answer found at Exporting data frame as PNG in ModelBuilder using ArcMap

I've followed the steps in the answer provided by @PolyGeo, but my output PNG is just a blank image.

I also added a few extra lines of code from ExportToPNG example 2 here to control the size of the PNG, because by default it's 640 by 480 pixels:

https://desktop.arcgis.com/en/arcmap/10.3/analyze/arcpy-mapping/exporttopng.htm

So my final code is:

import arcpy

lyrFile = arcpy.GetParameterAsText(0)
pngFile = arcpy.GetParameterAsText(1)

mxd = arcpy.mapping.MapDocument("D:/Old C Drive/School/Base Data/Scripts/Untitled.mxd")
df = arcpy.mapping.ListDataFrames(mxd,"Layers")[0]
addLayer = arcpy.mapping.Layer(lyrFile)
arcpy.mapping.ExportToPNG(mxd, pngFile, df,
    df_export_width=1920,
    df_export_height=1080)
del mxd

My mxd is totally empty, so I'm not sure where I went wrong. I did see in the original question someone mentioned that using a blank document didn't work for them either so they used another mxd and it worked. I tried that but no luck.

Answer 1

The code you used was originally from me, and I left out a line. I just tested the code below successfully using ArcMap 10.8.

import arcpy

lyrFile = r"C:\temp\testPolys.lyr"          
pngFile = r"C:\temp\testPolys.png"

mxd = arcpy.mapping.MapDocument(r"C:\temp\test.mxd")
df = arcpy.mapping.ListDataFrames(mxd,"Layers")[0]
addLayer = arcpy.mapping.Layer(lyrFile)
arcpy.mapping.AddLayer(df, addLayer)
arcpy.mapping.ExportToPNG(mxd, pngFile, df)
del mxd

The line I had forgotton to include was:

arcpy.mapping.AddLayer(df, addLayer)

I had made a Layer object (named addLayer) from the layer file, but forgot to add that Layer object as a new layer in my map. I have now corrected my answer on the original question accordingly.