示例#1
0
// from http://blog.gludion.com/2009/08/distance-to-quadratic-bezier-curve.html
// (currently only used by testing)
double SkDQuad::nearestT(const SkDPoint& pt) const {
    SkDVector pos = fPts[0] - pt;
    // search points P of bezier curve with PM.(dP / dt) = 0
    // a calculus leads to a 3d degree equation :
    SkDVector A = fPts[1] - fPts[0];
    SkDVector B = fPts[2] - fPts[1];
    B -= A;
    double a = B.dot(B);
    double b = 3 * A.dot(B);
    double c = 2 * A.dot(A) + pos.dot(B);
    double d = pos.dot(A);
    double ts[3];
    int roots = SkDCubic::RootsValidT(a, b, c, d, ts);
    double d0 = pt.distanceSquared(fPts[0]);
    double d2 = pt.distanceSquared(fPts[2]);
    double distMin = SkTMin(d0, d2);
    int bestIndex = -1;
    for (int index = 0; index < roots; ++index) {
        SkDPoint onQuad = ptAtT(ts[index]);
        double dist = pt.distanceSquared(onQuad);
        if (distMin > dist) {
            distMin = dist;
            bestIndex = index;
        }
    }
    if (bestIndex >= 0) {
        return ts[bestIndex];
    }
    return d0 < d2 ? 0 : 1;
}
示例#2
0
bool SkDCubic::controlsContainedByEnds() const {
    SkDVector startTan = fPts[1] - fPts[0];
    if (startTan.fX == 0 && startTan.fY == 0) {
        startTan = fPts[2] - fPts[0];
    }
    SkDVector endTan = fPts[2] - fPts[3];
    if (endTan.fX == 0 && endTan.fY == 0) {
        endTan = fPts[1] - fPts[3];
    }
    if (startTan.dot(endTan) >= 0) {
        return false;
    }
    SkDLine startEdge = {{fPts[0], fPts[0]}};
    startEdge[1].fX -= startTan.fY;
    startEdge[1].fY += startTan.fX;
    SkDLine endEdge = {{fPts[3], fPts[3]}};
    endEdge[1].fX -= endTan.fY;
    endEdge[1].fY += endTan.fX;
    double leftStart1 = startEdge.isLeft(fPts[1]);
    if (leftStart1 * startEdge.isLeft(fPts[2]) < 0) {
        return false;
    }
    double leftEnd1 = endEdge.isLeft(fPts[1]);
    if (leftEnd1 * endEdge.isLeft(fPts[2]) < 0) {
        return false;
    }
    return leftStart1 * leftEnd1 >= 0;
}