Transform image (or coordinates) based on perspective

[severo]

Give an option to "correct"/"invert" the perspective of a picture. See https://observablehq.com/d/c7a577c6f8664646 for a possible method + interactive controls.

[romsson]

This would be a great feature, with a couple of implications to make sure it can be done on mobile devices:

• Include an "edit" mode where the corners of the rectangle are active and draggable
• There should be an option to visualize the background either with or without the inverted perspective
• Isochrones should be drawn on both inverted and non inverted modes (but calculated should be done on the inverted mode)

[romsson]

An alternative to use a rectangle would be to use sliders like in Fil's example https://observablehq.com/d/e41898be08294e7c