1
2 /*
3 * Copyright 2011 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8 #include "SkMatrix.h"
9
10 // FIXME: needs to be in a header
11 bool SkSetPoly3To3_A(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]);
12
13 typedef double SkDScalar;
14
SkDScalar_toScalar(SkDScalar value)15 static SkScalar SkDScalar_toScalar(SkDScalar value) {
16 return static_cast<float>(value);
17 }
divide(SkDScalar numer,SkDScalar denom)18 static SkScalar divide(SkDScalar numer, SkDScalar denom) {
19 return static_cast<float>(numer / denom);
20 }
21
SkDScalar_setMul(SkScalar a,SkScalar b)22 static SkDScalar SkDScalar_setMul(SkScalar a, SkScalar b) {
23 return (SkDScalar) ((SkDScalar) a * b);
24 }
25
computeOuterProduct(SkScalar op[4],const SkPoint pts0[3],const SkPoint & ave0,const SkPoint pts1[3],const SkPoint & ave1)26 static void computeOuterProduct(SkScalar op[4],
27 const SkPoint pts0[3], const SkPoint& ave0,
28 const SkPoint pts1[3], const SkPoint& ave1) {
29 sk_bzero(op, 4 * sizeof(op[0]));
30 for (int i = 0; i < 3; i++) {
31 SkScalar x0 = pts0[i].fX - ave0.fX;
32 SkScalar y0 = pts0[i].fY - ave0.fY;
33 SkScalar x1 = pts1[i].fX - ave1.fX;
34 SkScalar y1 = pts1[i].fY - ave1.fY;
35 op[0] += SkScalarMul(x0, x1);
36 op[1] += SkScalarMul(x0, y1);
37 op[2] += SkScalarMul(y0, x1);
38 op[3] += SkScalarMul(y0, y1);
39 }
40 }
41
ddot(SkScalar ax,SkScalar ay,SkScalar bx,SkScalar by)42 static SkDScalar ddot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
43 return SkDScalar_setMul(ax, bx) + SkDScalar_setMul(ay, by);
44 }
45
dot(SkScalar ax,SkScalar ay,SkScalar bx,SkScalar by)46 static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
47 return SkDScalar_toScalar(ddot(ax, ay, bx, by));
48 }
49
SkSetPoly3To3_A(SkMatrix * matrix,const SkPoint src[3],const SkPoint dst[3])50 bool SkSetPoly3To3_A(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) {
51 const SkPoint& srcAve = src[0];
52 const SkPoint& dstAve = dst[0];
53
54 SkScalar srcOP[4], dstOP[4];
55
56 computeOuterProduct(srcOP, src, srcAve, src, srcAve);
57 computeOuterProduct(dstOP, src, srcAve, dst, dstAve);
58
59 SkDScalar det = SkDScalar_setMul(srcOP[0], srcOP[3]) -
60 SkDScalar_setMul(srcOP[1], srcOP[2]);
61
62 SkDScalar M[4];
63
64 const SkScalar srcOP0 = srcOP[3];
65 const SkScalar srcOP1 = -srcOP[1];
66 const SkScalar srcOP2 = -srcOP[2];
67 const SkScalar srcOP3 = srcOP[0];
68
69 M[0] = ddot(srcOP0, srcOP1, dstOP[0], dstOP[2]);
70 M[1] = ddot(srcOP2, srcOP3, dstOP[0], dstOP[2]);
71 M[2] = ddot(srcOP0, srcOP1, dstOP[1], dstOP[3]);
72 M[3] = ddot(srcOP2, srcOP3, dstOP[1], dstOP[3]);
73
74 matrix->reset();
75 matrix->setScaleX(divide(M[0], det));
76 matrix->setSkewX( divide(M[1], det));
77 matrix->setSkewY (divide(M[2], det));
78 matrix->setScaleY(divide(M[3], det));
79 matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY,
80 matrix->getScaleX(), matrix->getSkewX()));
81 matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY,
82 matrix->getSkewY(), matrix->getScaleY()));
83 return true;
84 }
85