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I have a polygon shapefile of geological units. Someone has already created a symbology and assigned standard colours to the units, available as a .lyr file.

What I need to do is create a list of the the 40+ units with their assigned RGB values using an ArcMap tool or maybe ArcPy.

I have been able to use polygon to raster, but it doesn't preserve the correct RGB values. That could be a feasible option and allow me to sample the colour if anyone has a suggestion on that path.

I have ArcGIS Desktop 10.5 Advanced License.

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  • Does your polygon file already have RGB values stored in a field or fields?
    – PolyGeo ♦
    Commented Jul 14, 2017 at 22:30
  • Is this a single layer file, classified by an attribute? And you want to get the RGB associated which each classification by attribute? What is your desired output format? A line of text + RGB value, ie- "MySoil- 120,35, 210" or something else?
    – RyanKDalton
    Commented Jul 14, 2017 at 22:34
  • Nope, not in the attribute table at least. Just a very specific colour ramp.
    – meguh78
    Commented Jul 14, 2017 at 22:39
  • RyanDalton Yes its a single shapefile, there's also the lyr file associated with it. The colours are classified by attribute (unit name). Yes to getting the RGB value associated with each classification. A text file would be fine.
    – meguh78
    Commented Jul 14, 2017 at 22:41

1 Answer 1

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  • Export colored polygons as png raster with world file.
  • Export result as grid format
  • add components of above as separate grids
  • Sample points inside polygons

enter image description here

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  • Thanks FelixIP, but it still does not export with the correct colours, which is the same problem I had when making a geotiff with the polygon to raster tool. The result is closer but still not correct. Do you know why this would be?
    – meguh78
    Commented Jul 18, 2017 at 19:25
  • Something to do with display color scheme. Perhaps play with outputs
    – FelixIP
    Commented Jul 18, 2017 at 19:32
  • Thanks for that, exporting the map as a .bmp + worldfile seemed to work, but only with the DPI way down (less than 75). The higher the DPI, the greater the divergence from the original colours for some reason. Also I double checked that the colour mode was set to 24-bit true colour.
    – meguh78
    Commented Jul 18, 2017 at 19:47

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