1#include "SkMatrix.h"
2
3typedef int64_t SkDScalar;
4
5static SkScalar SkDScalar_toScalar(SkDScalar value) {
6    SkDScalar result = (value + (1 << 15)) >> 16;
7    int top = result >> 31;
8    SkASSERT(top == 0 || top == -1);
9    return (SkScalar)result;
10}
11
12static SkDScalar SkDScalar_setMul(SkScalar a, SkScalar b) {
13    return (SkDScalar)a * b;
14}
15
16static void computeOuterProduct(SkMatrix* matrix,
17                                const SkPoint pts0[3], const SkPoint& ave0,
18                                const SkPoint pts1[3], const SkPoint& ave1) {
19    SkDScalar tmp[4];
20    sk_bzero(tmp, sizeof(tmp));
21
22    for (int i = 0; i < 3; i++) {
23        SkScalar x0 = pts0[i].fX - ave0.fX;
24        SkScalar y0 = pts0[i].fY - ave0.fY;
25        SkScalar x1 = pts1[i].fX - ave1.fX;
26        SkScalar y1 = pts1[i].fY - ave1.fY;
27        tmp[0] += SkDScalar_setMul(x0, x1);
28        tmp[1] += SkDScalar_setMul(x0, y1);
29        tmp[2] += SkDScalar_setMul(y0, x1);
30        tmp[3] += SkDScalar_setMul(y0, y1);
31    }
32    matrix->reset();
33    matrix->setScaleX(SkDScalar_toScalar(tmp[0]));
34    matrix->setSkewY( SkDScalar_toScalar(tmp[1]));
35    matrix->setSkewX( SkDScalar_toScalar(tmp[2]));
36    matrix->setScaleY(SkDScalar_toScalar(tmp[3]));
37}
38
39static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
40    return SkDScalar_toScalar(SkDScalar_setMul(ax, bx) +
41                              SkDScalar_setMul(ay, by));
42}
43
44bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) {
45    const SkPoint& srcAve = src[0];
46    const SkPoint& dstAve = dst[0];
47
48    SkMatrix srcOP, dstOP;
49
50    computeOuterProduct(&srcOP, src, srcAve, src, srcAve);
51
52    if (!srcOP.invert(&srcOP)) {
53        return false;
54    }
55
56    computeOuterProduct(&dstOP, src, srcAve, dst, dstAve);
57
58    matrix->setConcat(dstOP, srcOP);
59    matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY,
60                                    matrix->getScaleX(), matrix->getSkewX()));
61    matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY,
62                                    matrix->getSkewY(), matrix->getScaleY()));
63    return true;
64}
65
66