C++ SkVector::length方法代码示例

static SkScalar quad_folded_len(const SkPoint pts[3]) {
    SkScalar t = SkFindQuadMaxCurvature(pts);
    SkPoint pt = SkEvalQuadAt(pts, t);
    SkVector a = pts[2] - pt;
    SkScalar result = a.length();
    if (0 != t) {
        SkVector b = pts[0] - pt;
        result += b.length();
    }
    SkASSERT(SkScalarIsFinite(result));
    return result;
}

static void calc_dash_scaling(SkScalar* parallelScale, SkScalar* perpScale,
                            const SkMatrix& viewMatrix, const SkPoint pts[2]) {
    SkVector vecSrc = pts[1] - pts[0];
    SkScalar magSrc = vecSrc.length();
    SkScalar invSrc = magSrc ? SkScalarInvert(magSrc) : 0;
    vecSrc.scale(invSrc);

    SkVector vecSrcPerp;
    vecSrc.rotateCW(&vecSrcPerp);
    viewMatrix.mapVectors(&vecSrc, 1);
    viewMatrix.mapVectors(&vecSrcPerp, 1);

    // parallelScale tells how much to scale along the line parallel to the dash line
    // perpScale tells how much to scale in the direction perpendicular to the dash line
    *parallelScale = vecSrc.length();
    *perpScale = vecSrcPerp.length();
}

static void unitToPointsMatrix(const SkPoint pts[2], SkMatrix* matrix) {
    SkVector    vec = pts[1] - pts[0];
    SkScalar    mag = vec.length();
    SkScalar    inv = mag ? SkScalarInvert(mag) : 0;

    vec.scale(inv);
    matrix->setSinCos(vec.fY, vec.fX);
    matrix->preTranslate(pts[0].fX, pts[0].fY);
    matrix->preScale(mag, mag);
}

static void pts_to_unit_matrix(const SkPoint pts[2], SkMatrix* matrix) {
    SkVector    vec = pts[1] - pts[0];
    SkScalar    mag = vec.length();
    SkScalar    inv = mag ? SkScalarInvert(mag) : 0;

    vec.scale(inv);
    matrix->setSinCos(-vec.fY, vec.fX, pts[0].fX, pts[0].fY);
    matrix->postTranslate(-pts[0].fX, -pts[0].fY);
    matrix->postScale(inv, inv);
}

static void toUnitMatrix(const SkPoint pts[2], SkMatrix* matrix) {
    SkVector vec = pts[1] - pts[0];
    const float mag = vec.length();
    const float inv = mag ? 1.0f / mag : 0;

    vec.scale(inv);
    matrix->setSinCos(-vec.fY, vec.fX, pts[0].fX, pts[0].fY);
    matrix->postTranslate(-pts[0].fX, -pts[0].fY);
    matrix->postScale(inv, inv);
}

static SkMatrix pts_to_unit_matrix(const SkPoint pts[2]) {
    SkVector    vec = pts[1] - pts[0];
    SkScalar    mag = vec.length();
    SkScalar    inv = mag ? SkScalarInvert(mag) : 0;

    vec.scale(inv);
    SkMatrix matrix;
    matrix.setSinCos(-vec.fY, vec.fX, pts[0].fX, pts[0].fY);
    matrix.postTranslate(-pts[0].fX, -pts[0].fY);
    matrix.postScale(inv, inv);
    return matrix;
}

// calculates the rotation needed to aligned pts to the x axis with pts[0] < pts[1]
// Stores the rotation matrix in rotMatrix, and the mapped points in ptsRot
static void align_to_x_axis(const SkPoint pts[2], SkMatrix* rotMatrix, SkPoint ptsRot[2] = NULL) {
    SkVector vec = pts[1] - pts[0];
    SkScalar mag = vec.length();
    SkScalar inv = mag ? SkScalarInvert(mag) : 0;

    vec.scale(inv);
    rotMatrix->setSinCos(-vec.fY, vec.fX, pts[0].fX, pts[0].fY);
    if (ptsRot) {
        rotMatrix->mapPoints(ptsRot, pts, 2);
        // correction for numerical issues if map doesn't make ptsRot exactly horizontal
        ptsRot[1].fY = pts[0].fY;
    }
}

static void bloat_quad(const SkPoint qpts[3], const SkMatrix* toDevice,
                       const SkMatrix* toSrc, BezierVertex verts[kQuadNumVertices]) {
    SkASSERT(!toDevice == !toSrc);
    // original quad is specified by tri a,b,c
    SkPoint a = qpts[0];
    SkPoint b = qpts[1];
    SkPoint c = qpts[2];

    if (toDevice) {
        toDevice->mapPoints(&a, 1);
        toDevice->mapPoints(&b, 1);
        toDevice->mapPoints(&c, 1);
    }
    // make a new poly where we replace a and c by a 1-pixel wide edges orthog
    // to edges ab and bc:
    //
    //   before       |        after
    //                |              b0
    //         b      |
    //                |
    //                |     a0            c0
    // a         c    |        a1       c1
    //
    // edges a0->b0 and b0->c0 are parallel to original edges a->b and b->c,
    // respectively.
    BezierVertex& a0 = verts[0];
    BezierVertex& a1 = verts[1];
    BezierVertex& b0 = verts[2];
    BezierVertex& c0 = verts[3];
    BezierVertex& c1 = verts[4];

    SkVector ab = b;
    ab -= a;
    SkVector ac = c;
    ac -= a;
    SkVector cb = b;
    cb -= c;

    // We should have already handled degenerates
    SkASSERT(ab.length() > 0 && cb.length() > 0);

    ab.normalize();
    SkVector abN;
    abN.setOrthog(ab, SkVector::kLeft_Side);
    if (abN.dot(ac) > 0) {
        abN.negate();
    }

    cb.normalize();
    SkVector cbN;
    cbN.setOrthog(cb, SkVector::kLeft_Side);
    if (cbN.dot(ac) < 0) {
        cbN.negate();
    }

    a0.fPos = a;
    a0.fPos += abN;
    a1.fPos = a;
    a1.fPos -= abN;

    c0.fPos = c;
    c0.fPos += cbN;
    c1.fPos = c;
    c1.fPos -= cbN;

    intersect_lines(a0.fPos, abN, c0.fPos, cbN, &b0.fPos);

    if (toSrc) {
        toSrc->mapPointsWithStride(&verts[0].fPos, sizeof(BezierVertex), kQuadNumVertices);
    }
}