Function homography_from_4pt 

pub fn homography_from_4pt(
    src: &[Point2<f32>; 4],
    dst: &[Point2<f32>; 4],
) -> Option<Homography>

Compute H such that: dst ~ H * src (projective), using 4 point correspondences.

• src: points in “patch/cell” coords
• dst: points in image coords

Corner order must be consistent between src and dst.