I am experiencing this kind of visual defects for small polygons in Mapnik. These, in particular, are the small islands in the Pacific. As you see, instead of being uniform and nice, the borders have turned into some sort of dried bubble marks.

The .mss file used to generate this style for mapnik with kosmtik is very simple:

Map { background-color: #bbffff; }     
#countries { polygon-fill: #ffffba; line-color: #8dd; line-join: round; line-cap: round; line-width: 14; }

I have played with the line-join and line-cap properties, but this is the best result I have got and it is not enough.

Can this problem be solved at all? Am I missing something? Must something be done differently?

enter image description here

  • 1
    Line width of 14 feels quite big. Have you tried with width=1? – user30184 Jun 29 '18 at 12:41
  • Oh, well. That's the point. Line width 1 looks perfectly Ok. But I need the wide border for design purposes. For the looks, you know. To imitate the traditional coloring of seas around land masses. But maybe you can suggest another way to draw outlines around land in the sea? Maybe I am choosing the wrong approach for it? – tasOvted Jun 29 '18 at 12:50
  • By searching QGIS+outline I found this planet.qgis.org/planet/tag/outlines. – user30184 Jun 29 '18 at 13:15
  • Thanks a lot! That is some useful information for QGIS! Unfortunately, my problem is with Mapnik. Sorry for failing to make it sufficiently obvious. – tasOvted Jun 29 '18 at 14:30

From your comment that you want to draw a thick outline around the land masses, you can reduce your outline to 1 or even get rid of your outline and then use a buffer tool to draw a buffer around the land mass polygons. This might help with the way the outlines are being displayed.

  • Great suggestion! Thank you! Never used buffers in QGIS. Tried it and it is really useful thing, will certainly use it! ...Unfortunately my question was about Mapnik. It wasn't too obvious, my fault. Corrected the heading to reflect it. – tasOvted Jun 29 '18 at 14:28

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