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
11bool SkSetPoly3To3_A(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]);
12
13typedef double SkDScalar;
14
15static SkScalar SkDScalar_toScalar(SkDScalar value) {
16    return static_cast<float>(value);
17}
18static SkScalar divide(SkDScalar numer, SkDScalar denom) {
19    return static_cast<float>(numer / denom);
20}
21
22static SkDScalar SkDScalar_setMul(SkScalar a, SkScalar b) {
23    return (SkDScalar) ((SkDScalar) a * b);
24}
25
26static 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
42static SkDScalar ddot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
43    return SkDScalar_setMul(ax, bx) + SkDScalar_setMul(ay, by);
44}
45
46static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
47    return SkDScalar_toScalar(ddot(ax, ay, bx, by));
48}
49
50bool 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