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use pathops utils to improve precision of cubic chopping in scan converter

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BUG=skia:

Review URL: https://codereview.chromium.org/1113963002
This commit is contained in:
reed 2015-04-30 07:47:13 -07:00 committed by Commit bot
parent 30297c53bd
commit dc3088570f
5 changed files with 81 additions and 7 deletions
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37
src/core/SkEdgeClipper.cpp
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@ -225,6 +225,7 @@ bool SkEdgeClipper::clipQuad(const SkPoint srcPts[3], const SkRect& clip) {
///////////////////////////////////////////////////////////////////////////////
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
static SkScalar eval_cubic_coeff(SkScalar A, SkScalar B, SkScalar C,
SkScalar D, SkScalar t) {
return SkScalarMulAdd(SkScalarMulAdd(SkScalarMulAdd(A, t, B), t, C), t, D);
@ -274,23 +275,29 @@ static bool chopMonoCubicAtY(SkPoint pts[4], SkScalar y, SkScalar* t) {
static bool chopMonoCubicAtX(SkPoint pts[4], SkScalar x, SkScalar* t) {
return chopMonoCubicAt(pts[0].fX, pts[1].fX, pts[2].fX, pts[3].fX, x, t);
}
#endif
// Modify pts[] in place so that it is clipped in Y to the clip rect
static void chop_cubic_in_Y(SkPoint pts[4], const SkRect& clip) {
// are we partially above
if (pts[0].fY < clip.fTop) {
SkPoint tmp[7];
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
SkScalar t;
if (chopMonoCubicAtY(pts, clip.fTop, &t)) {
SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
// tmp[3, 4, 5].fY should all be to the below clip.fTop.
#else
if (SkChopMonoCubicAtY(pts, clip.fTop, tmp)) {
#endif
// tmp[3, 4].fY should all be to the below clip.fTop.
// Since we can't trust the numerics of
// the chopper, we force those conditions now
tmp[3].fY = clip.fTop;
clamp_ge(tmp[4].fY, clip.fTop);
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
clamp_ge(tmp[5].fY, clip.fTop);
#endif
pts[0] = tmp[3];
pts[1] = tmp[4];
@ -306,10 +313,14 @@ static void chop_cubic_in_Y(SkPoint pts[4], const SkRect& clip) {
// are we partially below
if (pts[3].fY > clip.fBottom) {
SkPoint tmp[7];
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
SkScalar t;
if (chopMonoCubicAtY(pts, clip.fBottom, &t)) {
SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
#else
if (SkChopMonoCubicAtY(pts, clip.fBottom, tmp)) {
#endif
tmp[3].fY = clip.fBottom;
clamp_le(tmp[2].fY, clip.fBottom);
@ -360,18 +371,24 @@ void SkEdgeClipper::clipMonoCubic(const SkPoint src[4], const SkRect& clip) {
// are we partially to the left
if (pts[0].fX < clip.fLeft) {
SkPoint tmp[7];
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
SkScalar t;
if (chopMonoCubicAtX(pts, clip.fLeft, &t)) {
SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
#else
if (SkChopMonoCubicAtX(pts, clip.fLeft, tmp)) {
#endif
this->appendVLine(clip.fLeft, tmp[0].fY, tmp[3].fY, reverse);
// tmp[3, 4, 5].fX should all be to the right of clip.fLeft.
// tmp[3, 4].fX should all be to the right of clip.fLeft.
// Since we can't trust the numerics of
// the chopper, we force those conditions now
tmp[3].fX = clip.fLeft;
clamp_ge(tmp[4].fX, clip.fLeft);
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
clamp_ge(tmp[5].fX, clip.fLeft);
#endif
pts[0] = tmp[3];
pts[1] = tmp[4];
@ -386,13 +403,19 @@ void SkEdgeClipper::clipMonoCubic(const SkPoint src[4], const SkRect& clip) {
// are we partially to the right
if (pts[3].fX > clip.fRight) {
SkPoint tmp[7];
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
SkScalar t;
if (chopMonoCubicAtX(pts, clip.fRight, &t)) {
SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
#else
if (SkChopMonoCubicAtX(pts, clip.fRight, tmp)) {
#endif
tmp[3].fX = clip.fRight;
clamp_le(tmp[2].fX, clip.fRight);
#ifdef SK_SUPPORT_LEGACY_CUBIC_CHOPPER
clamp_le(tmp[1].fX, clip.fRight);
#endif
this->appendCubic(tmp, reverse);
this->appendVLine(clip.fRight, tmp[3].fY, tmp[6].fY, reverse);

27
src/core/SkGeometry.cpp
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@ -916,6 +916,33 @@ int SkChopCubicAtMaxCurvature(const SkPoint src[4], SkPoint dst[13],
return count + 1;
}
#include "../pathops/SkPathOpsCubic.h"
typedef int (SkDCubic::*InterceptProc)(double intercept, double roots[3]) const;
static bool cubic_dchop_at_intercept(const SkPoint src[4], SkScalar intercept, SkPoint dst[7],
InterceptProc method) {
SkDCubic cubic;
double roots[3];
int count = (cubic.set(src).*method)(intercept, roots);
if (count > 0) {
SkDCubicPair pair = cubic.chopAt(roots[0]);
for (int i = 0; i < 7; ++i) {
dst[i] = pair.pts[i].asSkPoint();
}
return true;
}
return false;
}
bool SkChopMonoCubicAtY(SkPoint src[4], SkScalar y, SkPoint dst[7]) {
return cubic_dchop_at_intercept(src, y, dst, &SkDCubic::horizontalIntersect);
}
bool SkChopMonoCubicAtX(SkPoint src[4], SkScalar x, SkPoint dst[7]) {
return cubic_dchop_at_intercept(src, x, dst, &SkDCubic::verticalIntersect);
}
///////////////////////////////////////////////////////////////////////////////
/* Find t value for quadratic [a, b, c] = d.

3
src/core/SkGeometry.h
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@ -166,6 +166,9 @@ int SkFindCubicMaxCurvature(const SkPoint src[4], SkScalar tValues[3]);
int SkChopCubicAtMaxCurvature(const SkPoint src[4], SkPoint dst[13],
SkScalar tValues[3] = NULL);
bool SkChopMonoCubicAtX(SkPoint src[4], SkScalar y, SkPoint dst[7]);
bool SkChopMonoCubicAtY(SkPoint src[4], SkScalar x, SkPoint dst[7]);
enum SkCubicType {
kSerpentine_SkCubicType,
kCusp_SkCubicType,

10
src/pathops/SkDCubicLineIntersection.cpp
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@ -425,3 +425,13 @@ int SkIntersections::intersectRay(const SkDCubic& cubic, const SkDLine& line) {
}
return fUsed;
}
// SkDCubic accessors to Intersection utilities
int SkDCubic::horizontalIntersect(double yIntercept, double roots[3]) const {
return LineCubicIntersections::HorizontalIntersect(*this, yIntercept, roots);
}
int SkDCubic::verticalIntersect(double xIntercept, double roots[3]) const {
return LineCubicIntersections::VerticalIntersect(*this, xIntercept, roots);
}

11
src/pathops/SkPathOpsCubic.h
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@ -97,6 +97,17 @@ struct SkDCubic {
int searchRoots(double extremes[6], int extrema, double axisIntercept,
SearchAxis xAxis, double* validRoots) const;
/**
* Return the number of valid roots (0 < root < 1) for this cubic intersecting the
* specified horizontal line.
*/
int horizontalIntersect(double yIntercept, double roots[3]) const;
/**
* Return the number of valid roots (0 < root < 1) for this cubic intersecting the
* specified vertical line.
*/
int verticalIntersect(double xIntercept, double roots[3]) const;
const SkDCubic& set(const SkPoint pts[kPointCount]) {
fPts[0] = pts[0];
fPts[1] = pts[1];