Struct EdgeMap 

pub struct EdgeMap { /* private fields */ }

Per-pixel edge strength for one frozen frame, precomputed once.

Two maps, one per axis, quantized to u8 — a frame’s worth of f32 pairs is tens of megabytes per monitor, and the extra precision buys nothing when the answer is an integer pixel column.

Implementations

impl EdgeMap

pub fn new(gray: &GrayImage) -> Self

Detect edges in a frozen frame.

The operator is a forward difference — I(x) - I(x-1) — weighted 3:10:3 across the neighbouring rows in the Scharr manner. The weighting rejects single-pixel noise without smearing the edge’s position; the forward difference is what makes the position unambiguous. A centered difference peaks equally on both pixels of a one-pixel step, and a snap that lands on whichever of the two the cursor happened to approach from is not an answer a user can rely on. Position is the whole product here: an edge detected one pixel off is worse than no edge at all, because the user trusted it.

The convention this fixes is that a boundary sits on the first pixel of the new region. Snapping both sides of a 40px-wide button therefore gives 20 and 60, and the rect drawn between them is 40 wide — the button’s true width, not one pixel short.

pub const fn threshold(&self) -> u8

The strength a gradient must reach to count as an edge: the [EDGE_PERCENT] percentile of this frame’s own gradients, floored at MIN_GRADIENT.

Relative, because an absolute cut that works on a light theme finds nothing on a dark one. Floored, because a nearly blank screen’s 98th percentile is noise, and snapping to noise is worse than not snapping.

pub fn snap(&self, p: Point, radius: i32) -> Snap

Where p wants to go, searching radius pixels either way on each axis independently.

A non-positive radius disables snapping outright rather than searching a degenerate window.

pub fn snap_x(&self, p: Point, radius: i32) -> Option<SnapHit>

Just the vertical-edge search, for callers that move one axis at a time — sliding a shape sideways onto an alignment, say.

pub fn snap_y(&self, p: Point, radius: i32) -> Option<SnapHit>

Just the horizontal-edge search. See Self::snap_x.

Trait Implementations

impl Clone for EdgeMap

fn clone(&self) -> EdgeMap

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for EdgeMap

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.