==== Reduce Colours in GIMP ====

  * Select Colours - Poster Colours
  * Check Before/After image
  * the default is 3 colours, you can use the slider bar up to 256 colours to see the before/after diffence
  * In general a German CoA for instance can be reduced to below 10 colours
  * Maps with highlighted areas + CoA can often be reduced to below 15 colours, without visible difference
  * French CoA often have light effect, and therefore need more colours - sometimes 100
  * So it very much depends on the image, but the before/after will tell you how much you can reduce

==== Export the result ====

  * For the colour reduction to have an effect, you need to **export** the image to GIMP directory