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(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]); 12 13 static void computeOuterProduct(SkScalar op[4], 14 const SkPoint pts0[3], const SkPoint& ave0, 15 const SkPoint pts1[3], const SkPoint& ave1) { 16 sk_bzero(op, 4 * sizeof(op[0])); 17 for (int i = 0; i < 3; i++) { 18 SkScalar x0 = pts0[i].fX - ave0.fX; 19 SkScalar y0 = pts0[i].fY - ave0.fY; 20 SkScalar x1 = pts1[i].fX - ave1.fX; 21 SkScalar y1 = pts1[i].fY - ave1.fY; 22 op[0] += SkScalarMul(x0, x1); 23 op[1] += SkScalarMul(x0, y1); 24 op[2] += SkScalarMul(y0, x1); 25 op[3] += SkScalarMul(y0, y1); 26 } 27 } 28 29 static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) { 30 return SkScalarMul(ax, bx) + SkScalarMul(ay, by); 31 } 32 33 bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) { 34 const SkPoint& srcAve = src[0]; 35 const SkPoint& dstAve = dst[0]; 36 37 SkScalar srcOP[4], dstOP[4]; 38 39 computeOuterProduct(srcOP, src, srcAve, src, srcAve); 40 computeOuterProduct(dstOP, src, srcAve, dst, dstAve); 41 42 SkScalar det = SkScalarMul(srcOP[0], srcOP[3]) - SkScalarMul(srcOP[1], srcOP[2]); 43 44 // need SkScalarNearlyZeroSquared for this (to match Chrome's fix) 45 if (SkScalarNearlyZero(det)) { 46 return false; 47 } 48 49 SkScalar invDet = SkScalarInvert(det); 50 51 // now compute invDet * [srcOP]T * [dstOP] 52 53 // scale and transpose 54 const SkScalar srcOP0 = SkScalarMul( srcOP[3], invDet); 55 const SkScalar srcOP1 = SkScalarMul(-srcOP[1], invDet); 56 const SkScalar srcOP2 = SkScalarMul(-srcOP[2], invDet); 57 const SkScalar srcOP3 = SkScalarMul( srcOP[0], invDet); 58 59 matrix->reset(); 60 matrix->setScaleX(dot(srcOP0, srcOP1, dstOP[0], dstOP[2])); 61 matrix->setSkewX( dot(srcOP2, srcOP3, dstOP[0], dstOP[2])); 62 matrix->setSkewY (dot(srcOP0, srcOP1, dstOP[1], dstOP[3])); 63 matrix->setScaleY(dot(srcOP2, srcOP3, dstOP[1], dstOP[3])); 64 matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY, 65 matrix->getScaleX(), matrix->getSkewX())); 66 matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY, 67 matrix->getSkewY(), matrix->getScaleY())); 68 return true; 69 } 70
