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_D(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]);
12
13typedef int64_t SkDScalar;
14
15static SkScalar SkDScalar_toScalar(SkDScalar value) {
16    SkDScalar result = (value + (1 << 15)) >> 16;
17    SkDEBUGCODE(int top = static_cast<int>(result >> 31);)
18    SkASSERT(top == 0 || top == -1);
19    return (SkScalar)result;
20}
21
22static SkDScalar SkDScalar_setMul(SkScalar a, SkScalar b) {
23    return (SkDScalar) ((SkDScalar) a * (SkDScalar) b);
24}
25
26static void computeOuterProduct(SkMatrix* matrix,
27                                const SkPoint pts0[3], const SkPoint& ave0,
28                                const SkPoint pts1[3], const SkPoint& ave1) {
29    SkDScalar tmp[4];
30    sk_bzero(tmp, sizeof(tmp));
31
32    for (int i = 0; i < 3; i++) {
33        SkScalar x0 = pts0[i].fX - ave0.fX;
34        SkScalar y0 = pts0[i].fY - ave0.fY;
35        SkScalar x1 = pts1[i].fX - ave1.fX;
36        SkScalar y1 = pts1[i].fY - ave1.fY;
37        tmp[0] += SkDScalar_setMul(x0, x1);
38        tmp[1] += SkDScalar_setMul(x0, y1);
39        tmp[2] += SkDScalar_setMul(y0, x1);
40        tmp[3] += SkDScalar_setMul(y0, y1);
41    }
42    matrix->reset();
43    matrix->setScaleX(SkDScalar_toScalar(tmp[0]));
44    matrix->setSkewY( SkDScalar_toScalar(tmp[1]));
45    matrix->setSkewX( SkDScalar_toScalar(tmp[2]));
46    matrix->setScaleY(SkDScalar_toScalar(tmp[3]));
47}
48
49static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
50    return SkDScalar_toScalar(SkDScalar_setMul(ax, bx) +
51                              SkDScalar_setMul(ay, by));
52}
53
54bool SkSetPoly3To3_D(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) {
55    const SkPoint& srcAve = src[0];
56    const SkPoint& dstAve = dst[0];
57
58    SkMatrix srcOP, dstOP;
59
60    computeOuterProduct(&srcOP, src, srcAve, src, srcAve);
61
62    if (!srcOP.invert(&srcOP)) {
63        return false;
64    }
65
66    computeOuterProduct(&dstOP, src, srcAve, dst, dstAve);
67
68    matrix->setConcat(dstOP, srcOP);
69    matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY,
70                                    matrix->getScaleX(), matrix->getSkewX()));
71    matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY,
72                                    matrix->getSkewY(), matrix->getScaleY()));
73    return true;
74}
75