Feature request #19943
Extend algorithm only extends, but does not shorten lines
| Status: | Rejected | ||
|---|---|---|---|
| Priority: | Normal | ||
| Assignee: | - | ||
| Category: | Processing/Core | ||
| Pull Request or Patch supplied: | No | Resolution: | wontfix |
| Easy fix?: | No | Copied to github as #: | 27765 |
Description
Currently, there is an algorithm called Extend lines (visit documentation: https://docs.qgis.org/testing/en/docs/user_manual/processing_algs/qgis/vectorgeometry.html#extend-lines) which work great for extending lines, but I haven't been able to use it for reducing a line's length.
Example:
Provided a line with length=5m
If I use the following values: start distance = 2, end distance = 2, I get a new line with length=9 (5+2+2). Ok.
If, on the contrary, I use negative values (start distance = -2, end distance = -2), I do not get a new line with length=1 (5-2-2) as expected, but I get a line with the same length as the original one.
History
#1
Updated by Harrissou Santanna about 6 years ago
This is more a feature request than a bug report I think. I'm not sure that the Extend algorithm is supposed to shorten the lines (at least, I did not read such expectations in the linked documentation).
#2
Updated by Harrissou Santanna about 6 years ago
- Status changed from Open to Feedback
#3
Updated by Giovanni Manghi about 6 years ago
- Tracker changed from Bug report to Feature request
#4
Updated by Nyall Dawson about 6 years ago
- Status changed from Feedback to Rejected
- Resolution set to wontfix
There is a seperate algorithm for shrinking lines - "line substrings".
#5
Updated by Harrissou Santanna about 6 years ago
I had looked for it but obviously with wrong tags, hence https://github.com/qgis/QGIS/pull/8025
#6
Updated by Carlos Cámara about 6 years ago
I am using 3.2.3 and I can't find such line substring algorithm. I haven't found any reference on documentation, neither.
Since I have not used it, I am not sure how that algorithm works, but I would suggest reconsidering reopening this issue as a feature request if it does not work like that:
Imagine that I want to change the length of a line according to a field, which may be positive (extend) or negative (shrink). IMHO it would be great to solve this by using a single tool, not two different ones. I am not a programmer at all, but I cannot see any difference in changing a line's length while keeping its direction, no matter if that length is positive or negative.