Function singular_values

node-graph/libraries/rendering/src/renderer.rs:274–287

`(max, min)` factors by which a unit vector is stretched under `transform`'s linear part — the principal and minor singular values, equal to the semi-axes of the ellipse a unit circle maps to. Equivalent to `(max(sx, sy), min(sx, sy))` for axis-aligned scales, but accounts for shear.

(transform: DAffine2)

fn singular_values(transform: DAffine2) -> (f64, f64) {
	let m = transform.matrix2;
	let a = m.x_axis.x;
	let b = m.x_axis.y;
	let c = m.y_axis.x;
	let d = m.y_axis.y;
	// Eigenvalues of MᵀM via the closed form for a 2×2, both are non-negative
	let trace = a * a + b * b + c * c + d * d;
	let det = a * d - b * c;
	let discriminant = (trace * trace - 4. * det * det).max(0.).sqrt();
	let largest_eigenvalue = (trace + discriminant) * 0.5;
	let smallest_eigenvalue = ((trace - discriminant) * 0.5).max(0.);
	(largest_eigenvalue.sqrt(), smallest_eigenvalue.sqrt())
}

pub fn black_or_white_for_best_contrast(background: Option<Color>) -> Color {
	let Some(bg) = background else { return core_types::consts::LAYER_OUTLINE_STROKE_COLOR };

	let alpha = bg.a();