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      1 #include "SkMatrix.h"
      2 
      3 #ifdef SK_SCALAR_IS_FIXED
      4     typedef int64_t SkDScalar;
      5 
      6     static SkScalar SkDScalar_toScalar(SkDScalar value) {
      7         SkDScalar result = (value + (1 << 15)) >> 16;
      8         int top = result >> 31;
      9         SkASSERT(top == 0 || top == -1);
     10         return (SkScalar)result;
     11     }
     12     static SkScalar div(SkDScalar numer, SkDScalar denom) {
     13         denom >>= 16;
     14         return numer / denom;
     15     }
     16 #else
     17     typedef double SkDScalar;
     18 
     19     static SkScalar SkDScalar_toScalar(SkDScalar value) {
     20         return static_cast<float>(value);
     21     }
     22     static SkScalar div(SkDScalar numer, SkDScalar denom) {
     23         return static_cast<float>(numer / denom);
     24     }
     25 #endif
     26 
     27 static SkDScalar SkDScalar_setMul(SkScalar a, SkScalar b) {
     28     return (SkDScalar)a * b;
     29 }
     30 
     31 static void computeOuterProduct(SkScalar op[4],
     32                                 const SkPoint pts0[3], const SkPoint& ave0,
     33                                 const SkPoint pts1[3], const SkPoint& ave1) {
     34     sk_bzero(op, 4 * sizeof(op[0]));
     35     for (int i = 0; i < 3; i++) {
     36         SkScalar x0 = pts0[i].fX - ave0.fX;
     37         SkScalar y0 = pts0[i].fY - ave0.fY;
     38         SkScalar x1 = pts1[i].fX - ave1.fX;
     39         SkScalar y1 = pts1[i].fY - ave1.fY;
     40         op[0] += SkScalarMul(x0, x1);
     41         op[1] += SkScalarMul(x0, y1);
     42         op[2] += SkScalarMul(y0, x1);
     43         op[3] += SkScalarMul(y0, y1);
     44     }
     45 }
     46 
     47 static SkDScalar ddot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
     48     return SkDScalar_setMul(ax, bx) + SkDScalar_setMul(ay, by);
     49 }
     50 
     51 static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
     52     return SkDScalar_toScalar(ddot(ax, ay, bx, by));
     53 }
     54 
     55 bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) {
     56     const SkPoint& srcAve = src[0];
     57     const SkPoint& dstAve = dst[0];
     58 
     59     SkScalar srcOP[4], dstOP[4];
     60 
     61     computeOuterProduct(srcOP, src, srcAve, src, srcAve);
     62     computeOuterProduct(dstOP, src, srcAve, dst, dstAve);
     63 
     64     SkDScalar det = SkDScalar_setMul(srcOP[0], srcOP[3]) -
     65                     SkDScalar_setMul(srcOP[1], srcOP[2]);
     66 
     67     SkDScalar M[4];
     68 
     69     const SkScalar srcOP0 = srcOP[3];
     70     const SkScalar srcOP1 = -srcOP[1];
     71     const SkScalar srcOP2 = -srcOP[2];
     72     const SkScalar srcOP3 = srcOP[0];
     73 
     74     M[0] = ddot(srcOP0, srcOP1, dstOP[0], dstOP[2]);
     75     M[1] = ddot(srcOP2, srcOP3, dstOP[0], dstOP[2]);
     76     M[2] = ddot(srcOP0, srcOP1, dstOP[1], dstOP[3]);
     77     M[3] = ddot(srcOP2, srcOP3, dstOP[1], dstOP[3]);
     78 
     79     matrix->reset();
     80     matrix->setScaleX(div(M[0], det));
     81     matrix->setSkewX( div(M[1], det));
     82     matrix->setSkewY (div(M[2], det));
     83     matrix->setScaleY(div(M[3], det));
     84     matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY,
     85                                     matrix->getScaleX(), matrix->getSkewX()));
     86     matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY,
     87                                     matrix->getSkewY(), matrix->getScaleY()));
     88     return true;
     89 }
     90 
     91