reed@android.com | 8a1c16f | 2008-12-17 15:59:43 +0000 | [diff] [blame] | 1 | #include "SkMatrix.h" |
| 2 | |
| 3 | static void computeOuterProduct(SkScalar op[4], |
| 4 | const SkPoint pts0[3], const SkPoint& ave0, |
| 5 | const SkPoint pts1[3], const SkPoint& ave1) { |
reed@android.com | 4516f47 | 2009-06-29 16:25:36 +0000 | [diff] [blame] | 6 | sk_bzero(op, 4 * sizeof(op[0])); |
reed@android.com | 8a1c16f | 2008-12-17 15:59:43 +0000 | [diff] [blame] | 7 | for (int i = 0; i < 3; i++) { |
| 8 | SkScalar x0 = pts0[i].fX - ave0.fX; |
| 9 | SkScalar y0 = pts0[i].fY - ave0.fY; |
| 10 | SkScalar x1 = pts1[i].fX - ave1.fX; |
| 11 | SkScalar y1 = pts1[i].fY - ave1.fY; |
| 12 | op[0] += SkScalarMul(x0, x1); |
| 13 | op[1] += SkScalarMul(x0, y1); |
| 14 | op[2] += SkScalarMul(y0, x1); |
| 15 | op[3] += SkScalarMul(y0, y1); |
| 16 | } |
| 17 | } |
| 18 | |
| 19 | static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) { |
| 20 | return SkScalarMul(ax, bx) + SkScalarMul(ay, by); |
| 21 | } |
| 22 | |
| 23 | bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) { |
| 24 | const SkPoint& srcAve = src[0]; |
| 25 | const SkPoint& dstAve = dst[0]; |
| 26 | |
| 27 | SkScalar srcOP[4], dstOP[4]; |
| 28 | |
| 29 | computeOuterProduct(srcOP, src, srcAve, src, srcAve); |
| 30 | computeOuterProduct(dstOP, src, srcAve, dst, dstAve); |
| 31 | |
| 32 | SkScalar det = SkScalarMul(srcOP[0], srcOP[3]) - SkScalarMul(srcOP[1], srcOP[2]); |
| 33 | |
| 34 | // need SkScalarNearlyZeroSquared for this (to match Chrome's fix) |
| 35 | if (SkScalarNearlyZero(det)) { |
| 36 | return false; |
| 37 | } |
| 38 | |
| 39 | SkScalar invDet = SkScalarInvert(det); |
| 40 | |
| 41 | // now compute invDet * [srcOP]T * [dstOP] |
| 42 | |
| 43 | // scale and transpose |
| 44 | const SkScalar srcOP0 = SkScalarMul( srcOP[3], invDet); |
| 45 | const SkScalar srcOP1 = SkScalarMul(-srcOP[1], invDet); |
| 46 | const SkScalar srcOP2 = SkScalarMul(-srcOP[2], invDet); |
| 47 | const SkScalar srcOP3 = SkScalarMul( srcOP[0], invDet); |
| 48 | |
| 49 | matrix->reset(); |
| 50 | matrix->setScaleX(dot(srcOP0, srcOP1, dstOP[0], dstOP[2])); |
| 51 | matrix->setSkewX( dot(srcOP2, srcOP3, dstOP[0], dstOP[2])); |
| 52 | matrix->setSkewY (dot(srcOP0, srcOP1, dstOP[1], dstOP[3])); |
| 53 | matrix->setScaleY(dot(srcOP2, srcOP3, dstOP[1], dstOP[3])); |
| 54 | matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY, |
| 55 | matrix->getScaleX(), matrix->getSkewX())); |
| 56 | matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY, |
| 57 | matrix->getSkewY(), matrix->getScaleY())); |
| 58 | return true; |
| 59 | } |
| 60 | |