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Unified Diff: src/pathops/SkDLineIntersection.cpp

Issue 18058007: path ops work in progress (Closed) Base URL: https://skia.googlecode.com/svn/trunk
Patch Set: try try again Created 7 years, 5 months ago
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Index: src/pathops/SkDLineIntersection.cpp
diff --git a/src/pathops/SkDLineIntersection.cpp b/src/pathops/SkDLineIntersection.cpp
index 13c0dbbef42b82d33409f571af6d976f179f57aa..3b88b8870238ba63111d72084907d4de541dea93 100644
--- a/src/pathops/SkDLineIntersection.cpp
+++ b/src/pathops/SkDLineIntersection.cpp
@@ -75,13 +75,51 @@ int SkIntersections::intersectRay(const SkDLine& a, const SkDLine& b) {
return computePoints(a, used);
}
-/*
- Determine the intersection point of two line segments
- Return FALSE if the lines don't intersect
- from: http://paulbourke.net/geometry/lineline2d/
- */
+static bool checkEndPoint(double x, double y, const SkDLine& l, double* tPtr, int useX) {
+ if (!between(l[0].fX, x, l[1].fX) || !between(l[0].fY, y, l[1].fY)) {
+ return false;
+ }
+ double xLen = l[1].fX - l[0].fX;
+ double yLen = l[1].fY - l[0].fY;
+ if (useX < 0) {
+ useX = SkTAbs(xLen) > SkTAbs(yLen);
+ }
+ // OPTIMIZATION: do between test before divide
+ double t = useX ? (x - l[0].fX) / xLen : (y - l[0].fY) / yLen;
+ if (!between(0, t, 1)) {
+ return false;
+ }
+ double opp = useX ? (1 - t) * l[0].fY + t * l[1].fY : (1 - t) * l[0].fX + t * l[1].fX;
+ if (!AlmostEqualUlps(opp, useX ? y : x)) {
+ return false;
+ }
+ *tPtr = t;
+ return true;
+}
+// note that this only works if both lines are neither horizontal nor vertical
int SkIntersections::intersect(const SkDLine& a, const SkDLine& b) {
+ // see if end points intersect the opposite line
+ double t;
+ for (int iA = 0; iA < 2; ++iA) {
+ if (!checkEndPoint(a[iA].fX, a[iA].fY, b, &t, -1)) {
+ continue;
+ }
+ insert(iA, t, a[iA]);
+ }
+ for (int iB = 0; iB < 2; ++iB) {
+ if (!checkEndPoint(b[iB].fX, b[iB].fY, a, &t, -1)) {
+ continue;
+ }
+ insert(t, iB, b[iB]);
+ }
+ if (used() > 0) {
+ SkASSERT(fUsed <= 2);
+ return used(); // coincident lines are returned here
+ }
+ /* Determine the intersection point of two line segments
+ Return FALSE if the lines don't intersect
+ from: http://paulbourke.net/geometry/lineline2d/ */
double axLen = a[1].fX - a[0].fX;
double ayLen = a[1].fY - a[0].fY;
double bxLen = b[1].fX - b[0].fX;
@@ -105,64 +143,14 @@ int SkIntersections::intersect(const SkDLine& a, const SkDLine& b) {
&& !approximately_zero_inverse(numerB))) && !sk_double_isnan(numerA)
&& !sk_double_isnan(numerB)) {
if (mayNotOverlap) {
- return fUsed = 0;
+ return 0;
}
fT[0][0] = numerA;
fT[1][0] = numerB;
fPt[0] = a.xyAtT(numerA);
return computePoints(a, 1);
}
- /* See if the axis intercepts match:
- ay - ax * ayLen / axLen == by - bx * ayLen / axLen
- axLen * (ay - ax * ayLen / axLen) == axLen * (by - bx * ayLen / axLen)
- axLen * ay - ax * ayLen == axLen * by - bx * ayLen
- */
- if (!AlmostEqualUlps(axLen * a[0].fY - ayLen * a[0].fX,
- axLen * b[0].fY - ayLen * b[0].fX)) {
- return fUsed = 0;
- }
- const double* aPtr;
- const double* bPtr;
- if (fabs(axLen) > fabs(ayLen) || fabs(bxLen) > fabs(byLen)) {
- aPtr = &a[0].fX;
- bPtr = &b[0].fX;
- } else {
- aPtr = &a[0].fY;
- bPtr = &b[0].fY;
- }
- double a0 = aPtr[0];
- double a1 = aPtr[2];
- double b0 = bPtr[0];
- double b1 = bPtr[2];
- // OPTIMIZATION: restructure to reject before the divide
- // e.g., if ((a0 - b0) * (a0 - a1) < 0 || abs(a0 - b0) > abs(a0 - a1))
- // (except efficient)
- double aDenom = a0 - a1;
- if (approximately_zero(aDenom)) {
- if (!between(b0, a0, b1)) {
- return fUsed = 0;
- }
- fT[0][0] = fT[0][1] = 0;
- } else {
- double at0 = (a0 - b0) / aDenom;
- double at1 = (a0 - b1) / aDenom;
- if ((at0 < 0 && at1 < 0) || (at0 > 1 && at1 > 1)) {
- return fUsed = 0;
- }
- fT[0][0] = SkTMax(SkTMin(at0, 1.0), 0.0);
- fT[0][1] = SkTMax(SkTMin(at1, 1.0), 0.0);
- }
- double bDenom = b0 - b1;
- if (approximately_zero(bDenom)) {
- fT[1][0] = fT[1][1] = 0;
- } else {
- int bIn = aDenom * bDenom < 0;
- fT[1][bIn] = SkTMax(SkTMin((b0 - a0) / bDenom, 1.0), 0.0);
- fT[1][!bIn] = SkTMax(SkTMin((b0 - a1) / bDenom, 1.0), 0.0);
- }
- bool second = fabs(fT[0][0] - fT[0][1]) > FLT_EPSILON;
- SkASSERT((fabs(fT[1][0] - fT[1][1]) <= FLT_EPSILON) ^ second);
- return computePoints(a, 1 + second);
+ return 0;
}
int SkIntersections::horizontal(const SkDLine& line, double y) {
@@ -174,7 +162,7 @@ int SkIntersections::horizontal(const SkDLine& line, double y) {
if (min > y || max < y) {
return fUsed = 0;
}
- if (AlmostEqualUlps(min, max)) {
+ if (AlmostEqualUlps(min, max) && max - min < fabs(line[0].fX - line[1].fX)) {
fT[0][0] = 0;
fT[0][1] = 1;
return fUsed = 2;
@@ -183,42 +171,51 @@ int SkIntersections::horizontal(const SkDLine& line, double y) {
return fUsed = 1;
}
+static bool checkEndPointH(const SkDPoint& end, double left, double right,
+ double y, bool flipped, double* tPtr) {
+ if (!between(left, end.fX, right) || !AlmostEqualUlps(y, end.fY)) {
+ return false;
+ }
+ double t = (end.fX - left) / (right - left);
+ SkASSERT(between(0, t, 1));
+ *tPtr = flipped ? 1 - t : t;
+ return true;
+}
+
int SkIntersections::horizontal(const SkDLine& line, double left, double right,
double y, bool flipped) {
- int result = horizontal(line, y);
- switch (result) {
- case 0:
- break;
- case 1: {
- double xIntercept = line[0].fX + fT[0][0] * (line[1].fX - line[0].fX);
- if (!precisely_between(left, xIntercept, right)) {
- return fUsed = 0;
- }
- fT[1][0] = (xIntercept - left) / (right - left);
- break;
+ // see if end points intersect the opposite line
+ double t;
+ if (checkEndPoint(left, y, line, &t, true)) {
+ insert(t, flipped, left, y);
+ }
+ if (left != right) {
+ if (checkEndPoint(right, y, line, &t, true)) {
+ insert(t, !flipped, right, y);
}
- case 2:
- double a0 = line[0].fX;
- double a1 = line[1].fX;
- double b0 = flipped ? right : left;
- double b1 = flipped ? left : right;
- // FIXME: share common code below
- double at0 = (a0 - b0) / (a0 - a1);
- double at1 = (a0 - b1) / (a0 - a1);
- if ((at0 < 0 && at1 < 0) || (at0 > 1 && at1 > 1)) {
- return fUsed = 0;
+ for (int index = 0; index < 2; ++index) {
+ if (!checkEndPointH(line[index], left, right, y, flipped, &t)) {
+ continue;
}
- fT[0][0] = SkTMax(SkTMin(at0, 1.0), 0.0);
- fT[0][1] = SkTMax(SkTMin(at1, 1.0), 0.0);
- int bIn = (a0 - a1) * (b0 - b1) < 0;
- fT[1][bIn] = SkTMax(SkTMin((b0 - a0) / (b0 - b1), 1.0), 0.0);
- fT[1][!bIn] = SkTMax(SkTMin((b0 - a1) / (b0 - b1), 1.0), 0.0);
- bool second = fabs(fT[0][0] - fT[0][1]) > FLT_EPSILON;
- SkASSERT((fabs(fT[1][0] - fT[1][1]) <= FLT_EPSILON) ^ second);
- return computePoints(line, 1 + second);
+ insert(index, t, line[index]);
+ }
+ }
+ if (used() > 0) {
+ SkASSERT(fUsed <= 2);
+ return used(); // coincident lines are returned here
+ }
+ int result = horizontal(line, y);
+ if (!result) {
+ return 0;
+ }
+ SkASSERT(result == 1);
+ double xIntercept = line[0].fX + fT[0][0] * (line[1].fX - line[0].fX);
+ if (!precisely_between(left, xIntercept, right)) {
+ return fUsed = 0;
}
+ fT[1][0] = (xIntercept - left) / (right - left);
if (flipped) {
- // OPTIMIZATION: instead of swapping, pass original line, use [1].fX - [0].fX
+ // OPTIMIZATION: ? instead of swapping, pass original line, use [1].fX - [0].fX
for (int index = 0; index < result; ++index) {
fT[1][index] = 1 - fT[1][index];
}
@@ -244,40 +241,49 @@ int SkIntersections::vertical(const SkDLine& line, double x) {
return fUsed = 1;
}
+static bool checkEndPointV(const SkDPoint& end, double top, double bottom,
+ double x, bool flipped, double* tPtr) {
+ if (!between(top, end.fY, bottom) || !AlmostEqualUlps(x, end.fX)) {
+ return false;
+ }
+ double t = (end.fY - top) / (bottom - top);
+ SkASSERT(between(0, t, 1));
+ *tPtr = flipped ? 1 - t : t;
+ return true;
+}
+
int SkIntersections::vertical(const SkDLine& line, double top, double bottom,
- double x, bool flipped) {
- int result = vertical(line, x);
- switch (result) {
- case 0:
- break;
- case 1: {
- double yIntercept = line[0].fY + fT[0][0] * (line[1].fY - line[0].fY);
- if (!precisely_between(top, yIntercept, bottom)) {
- return fUsed = 0;
- }
- fT[1][0] = (yIntercept - top) / (bottom - top);
- break;
+ double x, bool flipped) {
+ // see if end points intersect the opposite line
+ double t;
+ if (checkEndPoint(x, top, line, &t, false)) {
+ insert(t, flipped, x, top);
+ }
+ if (top != bottom) {
+ if (checkEndPoint(x, bottom,line, &t, false)) {
+ insert(t, !flipped, x, bottom);
}
- case 2:
- double a0 = line[0].fY;
- double a1 = line[1].fY;
- double b0 = flipped ? bottom : top;
- double b1 = flipped ? top : bottom;
- // FIXME: share common code above
- double at0 = (a0 - b0) / (a0 - a1);
- double at1 = (a0 - b1) / (a0 - a1);
- if ((at0 < 0 && at1 < 0) || (at0 > 1 && at1 > 1)) {
- return fUsed = 0;
+ for (int index = 0; index < 2; ++index) {
+ if (!checkEndPointV(line[index], top, bottom, x, flipped, &t)) {
+ continue;
}
- fT[0][0] = SkTMax(SkTMin(at0, 1.0), 0.0);
- fT[0][1] = SkTMax(SkTMin(at1, 1.0), 0.0);
- int bIn = (a0 - a1) * (b0 - b1) < 0;
- fT[1][bIn] = SkTMax(SkTMin((b0 - a0) / (b0 - b1), 1.0), 0.0);
- fT[1][!bIn] = SkTMax(SkTMin((b0 - a1) / (b0 - b1), 1.0), 0.0);
- bool second = fabs(fT[0][0] - fT[0][1]) > FLT_EPSILON;
- SkASSERT((fabs(fT[1][0] - fT[1][1]) <= FLT_EPSILON) ^ second);
- return computePoints(line, 1 + second);
+ insert( index, t, line[index]);
+ }
+ }
+ if (used() > 0) {
+ SkASSERT(fUsed <= 2);
+ return used(); // coincident lines are returned here
+ }
+ int result = vertical(line, x);
+ if (!result) {
+ return 0;
+ }
+ SkASSERT(result == 1);
+ double yIntercept = line[0].fY + fT[0][0] * (line[1].fY - line[0].fY);
+ if (!precisely_between(top, yIntercept, bottom)) {
+ return fUsed = 0;
}
+ fT[1][0] = (yIntercept - top) / (bottom - top);
if (flipped) {
// OPTIMIZATION: instead of swapping, pass original line, use [1].fY - [0].fY
for (int index = 0; index < result; ++index) {
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