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* Copyright 2011 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include "SkMatrix.h"
// FIXME: needs to be in a header
bool SkSetPoly3To3_A(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]);
typedef double SkDScalar;
static SkScalar SkDScalar_toScalar(SkDScalar value) {
return static_cast<float>(value);
static SkScalar divide(SkDScalar numer, SkDScalar denom) {
return static_cast<float>(numer / denom);
static SkDScalar SkDScalar_setMul(SkScalar a, SkScalar b) {
return (SkDScalar) ((SkDScalar) a * b);
static void computeOuterProduct(SkScalar op[4],
const SkPoint pts0[3], const SkPoint& ave0,
const SkPoint pts1[3], const SkPoint& ave1) {
sk_bzero(op, 4 * sizeof(op[0]));
for (int i = 0; i < 3; i++) {
SkScalar x0 = pts0[i].fX - ave0.fX;
SkScalar y0 = pts0[i].fY - ave0.fY;
SkScalar x1 = pts1[i].fX - ave1.fX;
SkScalar y1 = pts1[i].fY - ave1.fY;
op[0] += SkScalarMul(x0, x1);
op[1] += SkScalarMul(x0, y1);
op[2] += SkScalarMul(y0, x1);
op[3] += SkScalarMul(y0, y1);
static SkDScalar ddot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
return SkDScalar_setMul(ax, bx) + SkDScalar_setMul(ay, by);
static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
return SkDScalar_toScalar(ddot(ax, ay, bx, by));
bool SkSetPoly3To3_A(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) {
const SkPoint& srcAve = src[0];
const SkPoint& dstAve = dst[0];
SkScalar srcOP[4], dstOP[4];
computeOuterProduct(srcOP, src, srcAve, src, srcAve);
computeOuterProduct(dstOP, src, srcAve, dst, dstAve);
SkDScalar det = SkDScalar_setMul(srcOP[0], srcOP[3]) -
SkDScalar_setMul(srcOP[1], srcOP[2]);
SkDScalar M[4];
const SkScalar srcOP0 = srcOP[3];
const SkScalar srcOP1 = -srcOP[1];
const SkScalar srcOP2 = -srcOP[2];
const SkScalar srcOP3 = srcOP[0];
M[0] = ddot(srcOP0, srcOP1, dstOP[0], dstOP[2]);
M[1] = ddot(srcOP2, srcOP3, dstOP[0], dstOP[2]);
M[2] = ddot(srcOP0, srcOP1, dstOP[1], dstOP[3]);
M[3] = ddot(srcOP2, srcOP3, dstOP[1], dstOP[3]);
matrix->setScaleX(divide(M[0], det));
matrix->setSkewX( divide(M[1], det));
matrix->setSkewY (divide(M[2], det));
matrix->setScaleY(divide(M[3], det));
matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY,
matrix->getScaleX(), matrix->getSkewX()));
matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY,
matrix->getSkewY(), matrix->getScaleY()));
return true;