Slicing by guidelines actually on an image

[rich2005]

Probably not practical, too many caveats depending on image and the nature of the dotted line.

Providing image does not contain too much of the line colour, the dotted line spacing is not too great and a little of the image lost

Using this plugin  ofn-extract-objects.py see  http://sourceforge.net/projects/gimp-too...s/scripts/ look for  ofn-extract-objects.zip dated 2020-09-13

Give the image an alpha channel for transparency Layer -> Transparency -> Add Alpha Channel
Color select the dotted line
Grow the selection by an amount to join up the selection
Cut the selection Edit -> Cut
Kill the selection Select -> None
Apply the plugin Layer -> Extract Objects

example of that https://i.imgur.com/sj0tsKX.mp4