| /* |
| * Copyright 2014 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "SkPoint.h" |
| |
| class SkMatrix; |
| |
| /** Find the Givens matrix G, which is the rotational matrix |
| * that rotates the vector h to the positive hoizontal axis. |
| * G * h = [hypot(h), 0] |
| * |
| * This is equivalent to |
| * |
| * SkScalar r = h.length(); |
| * SkScalar r_inv = r ? SkScalarInvert(r) : 0; |
| * h.scale(r_inv); |
| * G->setSinCos(-h.fY, h.fX); |
| * |
| * but has better numerical stability by using (partial) hypot, |
| * and saves a multiply by not computing r. |
| */ |
| void SkComputeGivensRotation(const SkVector& h, SkMatrix* G); |
