Add basic SVD support to SkMatrix. Allows you to pull out the x- and y-scale factors, sandwiched by…

include/core/SkMatrix.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkMatrix_DEFINED
@@ skipping 78 matching lines @@
         Returns false if other transformation types are included or is degenerate
      */
     bool isSimilarity(SkScalar tol = SK_ScalarNearlyZero) const;
 
     /** Returns true if the matrix contains only translation, rotation or scale
         (non-uniform scale is allowed).
         Returns false if other transformation types are included or is degenerate
      */
     bool preservesRightAngles(SkScalar tol = SK_ScalarNearlyZero) const;
 
+    /** Decomposes the upper 2x2 of the matrix into a rotation, followed by a non-uniform scale, 
+        followed by another rotation. Returns true if successful.
+        If the scale factors are uniform, then rotation1 will be 0.
+        If there is a reflection, yScale will be negative.
+        Returns false if the matrix is degenerate.

[reed1, 2013/07/18 14:15:54]

... or perspective?

+     */
+    bool decomposeUpper2x2(SkScalar* rotation0, 
+                           SkScalar* xScale, SkScalar* yScale, 
+                           SkScalar* rotation1) const;
+
     enum {
         kMScaleX,
         kMSkewX,
         kMTransX,
         kMSkewY,
         kMScaleY,
         kMTransY,
         kMPersp0,
         kMPersp1,
         kMPersp2
@@ skipping 556 matching lines @@
     static void RotTrans_pts(const SkMatrix&, SkPoint dst[], const SkPoint[],
                              int count);
     static void Persp_pts(const SkMatrix&, SkPoint dst[], const SkPoint[], int);
 
     static const MapPtsProc gMapPtsProcs[];
 
     friend class SkPerspIter;
 };
 
 #endif