Removing visual polygon borders in QGIS

Question

I have a GML layer representing a hexagonal grid that I would like to include in some maps. In QGIS 2.14.2 I applied a graduated style and completely removed the polygon border:

However, in the map canvas the borders are still being portrayed:

Zooming in one can see the border around each polygon, it is thin, but it is still there:

Suspecting this was an issue with the map canvas itself, I tried to produce some maps with the Print Composer. Even in vector format, the polygon borders are portrayed. Please check these files:

• PDF

• SVG

Is there any way to force QGIS to remove these borders?

Answer 1

The only way to that is to set the border color same as the fill color, then the border will disappear. You can keep setting the border line width is zero. Use 'Pick Color' to select exactly the same color from fill color.

Use Pick color to make the border color same as the filled color by selecting the filled color

The legend will look like this

And the final output is like this.

Answer 2

choropleth-gen

Tired of creating choropleths by hand for QGis I decided to create a little code package for the purpose. It has the suggestive name choropleth-gen and can be installed from PyPi, issuing a command like:

pip install choropleth-gen

The package installs two scripts in the system: gen_greyscale_choropleth and gen_spectral_choropleth. Both these scripts take the same arguments, identified with specific flags:

• -b - bottom value in the choropleth.
• -t - top value in the choropleth.
• -c - number of colour classes to generate.
• -o - path to the resulting SLD file.

Example:

gen_spectral_choropleth -b 10 -t 50 -c 20 -o style.sld

Answer 3

A way of doing this a little faster than @ahmadhanb (if you work with a color ramp for coloring) is to use the assistant by clicking on the symbol on the right and selecting "assistant"

In the "source" field you can insert the expression @symbol_color to receive the color that is used for the symbol's filling.

---

If you need other coloring schemes, you can insert this or other rules:

CASE
WHEN "FieldNameYouUseForColoring"<200 THEN 0
WHEN "FieldNameYouUseForColoring"<400 THEN 1
WHEN "FieldNameYouUseForColoring"<600 THEN 2
END

Next, restrict the range to (0,2) and select the color ramp you would like to select.

Answer 4

The Merged Features Renderer will let you render adjacent polygons as one polygon, while still being able to use sub-renderers such as the graduated or rule based ones. The polygons will appear as one, but can still be selected, labeled or identified individually.

If you have already set up a graduated renderer or a rule based renderer prior to switching to the Merged Features Renderer, the previous renderer will be turned into a sub-renderer of the Merged Features Renderer upon switching, with render settings such as rules and styles intact. Also, switching back from the Merged Features Renderer will transfer sub-renderer settings to the new rule based renderer. For graduated renderers etc., convert so rule based before switching back, to preserve classes/styles.

This is the simplest and fastes approach, and you don't have to set set border colors. The alternative approach, the same-color-hairline-border-workaround, in addition to require more work actually obscures parts of the neighbours, resulting in an unclear rendering of thin neighbour polygons when zooming out.