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 #include "SkMalloc.h" 10 11 // FIXME: needs to be in a header 12 bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]); 13 14 static void computeOuterProduct(SkScalar op[4], 15 const SkPoint pts0[3], const SkPoint& ave0, 16 const SkPoint pts1[3], const SkPoint& ave1) { 17 sk_bzero(op, 4 * sizeof(op[0])); 18 for (int i = 0; i < 3; i++) { 19 SkScalar x0 = pts0[i].fX - ave0.fX; 20 SkScalar y0 = pts0[i].fY - ave0.fY; 21 SkScalar x1 = pts1[i].fX - ave1.fX; 22 SkScalar y1 = pts1[i].fY - ave1.fY; 23 op[0] += x0 * x1; 24 op[1] += x0 * y1; 25 op[2] += y0 * x1; 26 op[3] += y0 * y1; 27 } 28 } 29 30 static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) { 31 return ax * bx + ay * by; 32 } 33 34 bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) { 35 const SkPoint& srcAve = src[0]; 36 const SkPoint& dstAve = dst[0]; 37 38 SkScalar srcOP[4], dstOP[4]; 39 40 computeOuterProduct(srcOP, src, srcAve, src, srcAve); 41 computeOuterProduct(dstOP, src, srcAve, dst, dstAve); 42 43 SkScalar det = srcOP[0] * srcOP[3] - srcOP[1] * srcOP[2]; 44 45 // need SkScalarNearlyZeroSquared for this (to match Chrome's fix) 46 if (SkScalarNearlyZero(det)) { 47 return false; 48 } 49 50 SkScalar invDet = SkScalarInvert(det); 51 52 // now compute invDet * [srcOP]T * [dstOP] 53 54 // scale and transpose 55 const SkScalar srcOP0 = srcOP[3] * invDet; 56 const SkScalar srcOP1 = -srcOP[1] * invDet; 57 const SkScalar srcOP2 = -srcOP[2] * invDet; 58 const SkScalar srcOP3 = srcOP[0] * invDet; 59 60 matrix->reset(); 61 matrix->setScaleX(dot(srcOP0, srcOP1, dstOP[0], dstOP[2])); 62 matrix->setSkewX( dot(srcOP2, srcOP3, dstOP[0], dstOP[2])); 63 matrix->setSkewY (dot(srcOP0, srcOP1, dstOP[1], dstOP[3])); 64 matrix->setScaleY(dot(srcOP2, srcOP3, dstOP[1], dstOP[3])); 65 matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY, 66 matrix->getScaleX(), matrix->getSkewX())); 67 matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY, 68 matrix->getSkewY(), matrix->getScaleY())); 69 return true; 70 } 71
