How to thicken the lines of an image?

Hello,

I don't know of any software that can modify the pattern of a raster drawing in that way. You can apply an effect (color) to the entire stroke but at the expense of sharpness. You can choose the pencil, its size, density, and color at the time of drawing, but I'm not sure you can modify these elements on an already completed stroke.

I haven't explored the possibilities of software like Krita, which reads WEBP files like yours.

https://krita.org/fr/fonctionnalites/points-forts/

However, it seems to me that it would be better to consider transforming your imported raster drawing into a vector drawing where you have the option to change the parameters of a complete drawing or its components, but I have only tested this on a drawing created from scratch, not from a map.

https://inkscape.org/fr/

That said, I don't know what software you use to color your maps, but the line I see, even if thin, should allow you to fill each of the surfaces without any problem.

Try with Inkscape or PhotoFiltre (free version).

Corel Draw (raster/vector) should be capable of it.

Hello,

In addition to the very thorough explanation from Georges97, I see that your image comes from d-maps.com. You can download the image in .svg format and edit it using Illustrator, among other tools, to "easily" manage the thickness of the contours.

Hello,

With time, patience, and above all a lot of dexterity

Under photofiltre.

---

Hello everyone.

I applaud the great work of jag72 but, being less brave, I prefer the solution of squel8 which requires no software to modify the border thickness.
You just need to modify the svg file with a text editor: line 11 variable stroke-width as follows:

.str0 {stroke:black;stroke-width:30;stroke-miterlimit:22.9256}<!--border thickness-->

Happy Monday