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I've used QGIS's Polygonize to convert the following raster into outlines. The polygonize tool does produce a vector output, but it isn't in plain polygon form but some thousands of single pixel polygons.

The results of QGIS Polygonize

I understand that this is the expected behavior of the Polygonize tool and one can now simplify these weird squares for it to just be two polygons - one for brown and one for purple. I tried setting a really low threshold of 0.000001 for v.generalize (in the Processing toolbox) for these shapes to be converted into a line and yet there seems to be no improvement. The documentation of v.generalize did not seem too useful.

How does one go about making this into two plain polygons?

  • Erm, v.generalize needs a larger value to mash polygons up. Small values lead to keeping status quo. – Erik Feb 5 at 13:15
  • I see! even a higher value such as 1000 or 100000, isn't doing anything different except, I now have an extra layer called error generated - which is just points. – user10046100 Feb 6 at 8:05
  • So, your raster has only two distinct areas you want to vectorize? Or are there other classes, too? – Erik Feb 6 at 8:07
  • There are other classes; I actually ended up converting the raster to a SVG on Illustrator and then used polygonize to raster it and then just selected the shapes and created a new layer with the shapes I wanted. – user10046100 Feb 6 at 8:22

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