Gradient colour for lines

Question

My road network is broken up into segments. I want to produce a map that shows where the segments start and finish.

I don't really want to create a point layer that shows the location of the ends of each line, but will if I have to. And I know that I could categorise segments and use a colour ramp or random colours, but I was looking for something that would look a little more classy.

I was wondering if there is a way to use a colour ramp - or gradient fill - for lines in QGIS? What I envisage is every line segment starts with one colour and finishes with another colour. This would also serve to indicate line direction - another one of my requirements.

Any ideas? Johanna

Answer 1

In the moment there is no way to colour lines with a gradient style.

First buffer your linestrings. Then you can set a gradient colour for the buffer polygons.

Here is a HowTo: How to visualize measure values along linestrings in QGIS?

Another Idea

requirement: your lines have an disinct ID

1. Cut your linestrings in very small substrings (that it looks like a gradient).

   "______" linestring with id 1 and 100m

   "----------" every single substring must have a distinct id or serial number. Here 1 to 10 (one substring 10m). When all the linestrings have the same direction it would start with 1 und end up with the maximum count of substring.

   2. Categorize the substrings and use a color ramp: 1 green 10 (n substrings) red

Problem could be the large amount of classes, if you have very long linestrings.

Answer 2

If your polylines is dense enough and of single type, you could use this approach:

1. Set a "Single symbol" as symbolizer
2. Change symbol layer type of a line to "Geometry generator" with type "LineString/MultiLineString"
3. Set segments_to_lines($geometry) as expression. This function breaks your line into two-point segments and returns multigeometry
4. Now you can set symbol for every generated segment. Go to symbology page of generated segments and change color expression to: ramp_color('Spectral', @geometry_part_num / @geometry_part_count). "Spectral" is the name of color ramp, you can find others in drop-down list of colors on graduated symbology page.

As a result you'll get something like this:

Another option is to set a basic color for line and then use lighter/darker functions for every segment.