Extending lines to their Bounding Box in QGIS

Question

How to extend lines to Bounding Box in QGIS as in the following image:

Figure 1: Lines

Figure 2: Lines extended to Bounding Box
Link to Shapefile of Bounding Box: https://drive.google.com/drive/folders/1jsJ8m2dG0DNwF1jepxpWzwfUVI5sVJJe?usp=sharing
Link to shapefile of lines: https://drive.google.com/drive/folders/1BQvrMiPillL5ubYsDHfEyoV9st12z0E9?usp=sharing

Babel · Answer

Use this expression with geometry generator or the Geometry by expression tool - the expression is adapted to the data you provided (layer name: 'Bounding Box', distance to extend the line: 65):
intersection (
    extend (
        $geometry,65,65
    ),
    geometry (
        get_feature_by_id(
            'Bounding Box',0
        )
    )
)

Nil · Answer

It may not be the most elegant way. However, you use  "Extend line" to extend lines by the distance of the longest edge of the polygon.

The output looks like this and you can clip by Polygon with the "Intersection" tool.

And the output looks like this

Extending lines to their Bounding Box in QGIS

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