pub fn extract_board(
quads: &[LinkedQuad],
coords: &HashMap<usize, QuadGrid>,
pattern_w: usize,
pattern_h: usize,
) -> Option<Vec<(f32, f32)>>Expand description
Validate and extract a pattern_w x pattern_h board from a lattice-assigned
connected component.
The reliable inner corners (referenced by >= 2 quads) must span a
pattern_w x pattern_h lattice rectangle. Interior corners missing from
that rectangle (because a neighboring square was not detected) are filled
in — analogous to OpenCV’s board augmentation: a corner referenced by a
single quad is taken directly, otherwise its position is predicted from a
homography fit to the reliable corners (lattice -> pixel). The caller’s
sub-pixel refinement then snaps any predicted corner to the true saddle.
Returns the corners row-major (lattice row then column), after a monotonicity check.