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I have Four columns like MapCode R G B, I would like to create my own colour from the attribute table(R, G, B-Column) for Mapcode.

I would like to apply symbology based on MapCode values(which is unique) and I have the color Values (R, G, B,) as seprate Columns in the same table. how to create color ramps for unique map_code

MapCode, R, G, B


AB1C, 243, 255, 128


BB12, 124, 125, 120


enter image description here

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  • Not really sure what you want to do. Can you explain a little further? To get a color from your columns use data defined override and an expression like "R"||','||"G"||','||"B"||','||255. May I ask what you want to do with python and plugins?
    – MrXsquared
    May 30 '19 at 18:06
  • I would like to apply symbology based on MapCode values(which is unique) and I have the color Values (R, G, B,) as seprate Columns in the same table, is there any plugins or python code available to do that
    – Gobinath
    May 30 '19 at 18:09
  • You dont need plugins to do that. Data defined symbology definition is a core feature of QGIS. Possible using python too, but as I interpret your question, there is no need for it. Can you give an example how a symbol shall look like when MapCode is AB1C and how if MapCode is BB12?
    – MrXsquared
    May 30 '19 at 18:14
  • can u please have a look on that pic so that it will be easy to understand
    – Gobinath
    May 30 '19 at 18:25
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Go to the Layer Properties and the Symbology tab

Depending on the layer type just select a simple fill, or a simple line instead of a categorized symbol.

Next to the "Fill color" or "Stroke color" whatever you are wanting colored, and there is a drop down select next to it. Select Edit... from the drop down which will bring up the Expression String Builder

enter image description here

Put in this expression color_rgb( "R","G","B")

where "R" "G" and "B" represent the column names that contain your RGB values.

I added some random RGB values to a USA state layer and this was the result

USA random assigned colors

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  • Thanks, @TJ Rockefeller., It works for me but still, I have problems while exporting for web(using qgis2web plugin) it takes only one colour not the classified colours everything shows a single colour. how do I rectify this problem?
    – Gobinath
    Jun 3 '19 at 11:21
  • @Gobinath Sorry to hear that this isn't working for export to the web. I don't have any experience with the qgis2web plugin, and you may need to ask another question specific to qgis2web. Jun 3 '19 at 13:22
  • Thank you. @TJ Rockefeller ... I'll rise one more question with detailed screenshots... Thank you very much
    – Gobinath
    Jun 3 '19 at 13:24

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