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When I create a map, which uses 13 different colors (12 + gray for background), why uses(!!) QGIS more than 20000 different colors when saved as bmp, png or jpg?- I verified this behaviour with irfanview (image | information , used colors). As gif as an export-option is not available, how can I limit the number of used colors in the exported raster-files. reducing later in irfanview is not an option, because colors are also changed (e.g. replaced, dithered,...) not only eliminated.

I use QGIS 2.18.13 64bit under windows 10

enter image description here

  • can you export as png8? – nmtoken Sep 18 '17 at 19:38
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    What about turning off antialiasing? – ndawson Sep 19 '17 at 4:00
  • @ndawson: thx, this is the solution, now I have only 13 used colors. If you post your comment as answer I can accept your answer – Kurt Sep 19 '17 at 4:54
  • @nmtoken as far as i now there is no export option png8 – Kurt Sep 19 '17 at 4:55
  • It's looks like that you need indexed colours. The GIF format is most suitable for this. – Dmitry Baryshnikov Sep 19 '17 at 7:15
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It's likely caused by the antialiasing used by default. If you turn it off from settings -> options -> rendering -> "Make lines appear less jagged at the expense of some rendering performance" then the output will ONLY have the selected colors, and not the "in between" shades used by antialiasing.

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