3 * Copyright 2008 The Android Open Source Project
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
10 #include "SkMathPriv.h"
13 void SkIPoint::rotateCW(SkIPoint* dst) const {
16 // use a tmp in case this == dst
22 void SkIPoint::rotateCCW(SkIPoint* dst) const {
25 // use a tmp in case this == dst
31 ///////////////////////////////////////////////////////////////////////////////
33 void SkPoint::setIRectFan(int l, int t, int r, int b, size_t stride) {
34 SkASSERT(stride >= sizeof(SkPoint));
36 ((SkPoint*)((intptr_t)this + 0 * stride))->set(SkIntToScalar(l),
38 ((SkPoint*)((intptr_t)this + 1 * stride))->set(SkIntToScalar(l),
40 ((SkPoint*)((intptr_t)this + 2 * stride))->set(SkIntToScalar(r),
42 ((SkPoint*)((intptr_t)this + 3 * stride))->set(SkIntToScalar(r),
46 void SkPoint::rotateCW(SkPoint* dst) const {
49 // use a tmp in case this == dst
55 void SkPoint::rotateCCW(SkPoint* dst) const {
58 // use a tmp in case this == dst
64 void SkPoint::scale(SkScalar scale, SkPoint* dst) const {
66 dst->set(SkScalarMul(fX, scale), SkScalarMul(fY, scale));
69 bool SkPoint::normalize() {
70 return this->setLength(fX, fY, SK_Scalar1);
73 bool SkPoint::setNormalize(SkScalar x, SkScalar y) {
74 return this->setLength(x, y, SK_Scalar1);
77 bool SkPoint::setLength(SkScalar length) {
78 return this->setLength(fX, fY, length);
81 // Returns the square of the Euclidian distance to (dx,dy).
82 static inline float getLengthSquared(float dx, float dy) {
83 return dx * dx + dy * dy;
86 // Calculates the square of the Euclidian distance to (dx,dy) and stores it in
87 // *lengthSquared. Returns true if the distance is judged to be "nearly zero".
89 // This logic is encapsulated in a helper method to make it explicit that we
90 // always perform this check in the same manner, to avoid inconsistencies
91 // (see http://code.google.com/p/skia/issues/detail?id=560 ).
92 static inline bool isLengthNearlyZero(float dx, float dy,
93 float *lengthSquared) {
94 *lengthSquared = getLengthSquared(dx, dy);
95 return *lengthSquared <= (SK_ScalarNearlyZero * SK_ScalarNearlyZero);
98 SkScalar SkPoint::Normalize(SkPoint* pt) {
102 if (isLengthNearlyZero(x, y, &mag2)) {
107 if (SkScalarIsFinite(mag2)) {
108 mag = sk_float_sqrt(mag2);
111 // our mag2 step overflowed to infinity, so use doubles instead.
112 // much slower, but needed when x or y are very large, other wise we
113 // divide by inf. and return (0,0) vector.
116 double magmag = sqrt(xx * xx + yy * yy);
118 // we perform the divide with the double magmag, to stay exactly the
119 // same as setLength. It would be faster to perform the divide with
120 // mag, but it is possible that mag has overflowed to inf. but still
121 // have a non-zero value for scale (thanks to denormalized numbers).
122 scale = (float)(1 / magmag);
124 pt->set(x * scale, y * scale);
128 SkScalar SkPoint::Length(SkScalar dx, SkScalar dy) {
129 float mag2 = dx * dx + dy * dy;
130 if (SkScalarIsFinite(mag2)) {
131 return sk_float_sqrt(mag2);
135 return (float)sqrt(xx * xx + yy * yy);
140 * We have to worry about 2 tricky conditions:
141 * 1. underflow of mag2 (compared against nearlyzero^2)
142 * 2. overflow of mag2 (compared w/ isfinite)
144 * If we underflow, we return false. If we overflow, we compute again using
145 * doubles, which is much slower (3x in a desktop test) but will not overflow.
147 bool SkPoint::setLength(float x, float y, float length) {
149 if (isLengthNearlyZero(x, y, &mag2)) {
154 if (SkScalarIsFinite(mag2)) {
155 scale = length / sk_float_sqrt(mag2);
157 // our mag2 step overflowed to infinity, so use doubles instead.
158 // much slower, but needed when x or y are very large, other wise we
159 // divide by inf. and return (0,0) vector.
162 #ifdef SK_DISCARD_DENORMALIZED_FOR_SPEED
163 // The iOS ARM processor discards small denormalized numbers to go faster.
164 // Casting this to a float would cause the scale to go to zero. Keeping it
165 // as a double for the multiply keeps the scale non-zero.
166 double dscale = length / sqrt(xx * xx + yy * yy);
171 scale = (float)(length / sqrt(xx * xx + yy * yy));
179 bool SkPoint::setLengthFast(float length) {
180 return this->setLengthFast(fX, fY, length);
183 bool SkPoint::setLengthFast(float x, float y, float length) {
185 if (isLengthNearlyZero(x, y, &mag2)) {
190 if (SkScalarIsFinite(mag2)) {
191 scale = length * sk_float_rsqrt(mag2); // <--- this is the difference
193 // our mag2 step overflowed to infinity, so use doubles instead.
194 // much slower, but needed when x or y are very large, other wise we
195 // divide by inf. and return (0,0) vector.
198 scale = (float)(length / sqrt(xx * xx + yy * yy));
206 ///////////////////////////////////////////////////////////////////////////////
208 SkScalar SkPoint::distanceToLineBetweenSqd(const SkPoint& a,
213 SkVector v = *this - a;
215 SkScalar uLengthSqd = u.lengthSqd();
216 SkScalar det = u.cross(v);
218 SkASSERT(-1 == SkPoint::kLeft_Side &&
219 0 == SkPoint::kOn_Side &&
221 *side = (Side) SkScalarSignAsInt(det);
223 return SkScalarMulDiv(det, det, uLengthSqd);
226 SkScalar SkPoint::distanceToLineSegmentBetweenSqd(const SkPoint& a,
227 const SkPoint& b) const {
228 // See comments to distanceToLineBetweenSqd. If the projection of c onto
229 // u is between a and b then this returns the same result as that
230 // function. Otherwise, it returns the distance to the closer of a and
231 // b. Let the projection of v onto u be v'. There are three cases:
232 // 1. v' points opposite to u. c is not between a and b and is closer
234 // 2. v' points along u and has magnitude less than y. c is between
235 // a and b and the distance to the segment is the same as distance
237 // 3. v' points along u and has greater magnitude than u. c is not
238 // not between a and b and is closer to b than a.
239 // v' = (u dot v) * u / |u|. So if (u dot v)/|u| is less than zero we're
240 // in case 1. If (u dot v)/|u| is > |u| we are in case 3. Otherwise
241 // we're in case 2. We actually compare (u dot v) to 0 and |u|^2 to
242 // avoid a sqrt to compute |u|.
245 SkVector v = *this - a;
247 SkScalar uLengthSqd = u.lengthSqd();
248 SkScalar uDotV = SkPoint::DotProduct(u, v);
251 return v.lengthSqd();
252 } else if (uDotV > uLengthSqd) {
253 return b.distanceToSqd(*this);
255 SkScalar det = u.cross(v);
256 return SkScalarMulDiv(det, det, uLengthSqd);