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| 1 /* | |
| 2 * Copyright 2016 ARM Ltd. | |
| 3 * | |
| 4 * Use of this source code is governed by a BSD-style license that can be | |
| 5 * found in the LICENSE file. | |
| 6 */ | |
| 7 | |
| 8 #include "GrDistanceFieldGenFromVector.h" | |
| 9 #include "SkPoint.h" | |
| 10 #include "SkGeometry.h" | |
| 11 #include "SkPathOps.h" | |
| 12 #include "GrPathUtils.h" | |
| 13 #include "GrConfig.h" | |
| 14 | |
| 15 /** | |
| 16 * If a scanline (a row of texel) cross from the kRight_SegSide | |
| 17 * of a segment to the kLeft_SegSide, the winding score should | |
| 18 * add 1. | |
| 19 * And winding score should subtract 1 if the scanline cross | |
| 20 * from kLeft_SegSide to kRight_SegSide. | |
| 21 * Always return kNA_SegSide if the scanline does not cross over | |
| 22 * the segment. Winding score should be zero in this case. | |
| 23 * You can get the winding number for each texel of the scanline | |
| 24 * by adding the winding score from left to right. | |
| 25 * Assuming we always start from outside, so the winding number | |
| 26 * should always start from zero. | |
| 27 * ________ ________ | |
| 28 * | | | | | |
| 29 * ...R|L......L|R.....L|R......R|L..... <= Scanline & side of segment | |
| 30 * |+1 |-1 |-1 |+1 <= Winding score | |
| 31 * 0 | 1 ^ 0 ^ -1 |0 <= Winding number | |
| 32 * |________| |________| | |
| 33 * | |
| 34 * .......NA................NA.......... | |
| 35 * 0 0 | |
| 36 */ | |
| 37 enum SegSide { | |
| 38 kLeft_SegSide = -1, | |
| 39 kOn_SegSide = 0, | |
| 40 kRight_SegSide = 1, | |
| 41 kNA_SegSide = 2, | |
| 42 }; | |
| 43 | |
| 44 struct DFData { | |
| 45 float fDistSq; // distance squared to nearest (so far) edge | |
| 46 int fDeltaWindingScore; // +1 or -1 whenever a scanline cross over a segme
nt | |
| 47 }; | |
| 48 | |
| 49 /////////////////////////////////////////////////////////////////////////////// | |
| 50 | |
| 51 /* | |
| 52 * Type definition for double precision DPoint and DAffineMatrix | |
| 53 */ | |
| 54 | |
| 55 // Point with double precision | |
| 56 struct DPoint { | |
| 57 double fX, fY; | |
| 58 | |
| 59 static DPoint Make(double x, double y) { | |
| 60 DPoint pt; | |
| 61 pt.set(x, y); | |
| 62 return pt; | |
| 63 } | |
| 64 | |
| 65 double x() const { return fX; } | |
| 66 double y() const { return fY; } | |
| 67 | |
| 68 void set(double x, double y) { fX = x; fY = y; } | |
| 69 | |
| 70 /** Returns the euclidian distance from (0,0) to (x,y) | |
| 71 */ | |
| 72 static double Length(double x, double y) { | |
| 73 return sqrt(x * x + y * y); | |
| 74 } | |
| 75 | |
| 76 /** Returns the euclidian distance between a and b | |
| 77 */ | |
| 78 static double Distance(const DPoint& a, const DPoint& b) { | |
| 79 return Length(a.fX - b.fX, a.fY - b.fY); | |
| 80 } | |
| 81 | |
| 82 double distanceToSqd(const DPoint& pt) const { | |
| 83 double dx = fX - pt.fX; | |
| 84 double dy = fY - pt.fY; | |
| 85 return dx * dx + dy * dy; | |
| 86 } | |
| 87 }; | |
| 88 | |
| 89 // Matrix with double precision for affine transformation. | |
| 90 // We don't store row 3 because its always (0, 0, 1). | |
| 91 class DAffineMatrix { | |
| 92 public: | |
| 93 double operator[](int index) const { | |
| 94 SkASSERT((unsigned)index < 6); | |
| 95 return fMat[index]; | |
| 96 } | |
| 97 | |
| 98 double& operator[](int index) { | |
| 99 SkASSERT((unsigned)index < 6); | |
| 100 return fMat[index]; | |
| 101 } | |
| 102 | |
| 103 void setAffine(double m11, double m12, double m13, | |
| 104 double m21, double m22, double m23) { | |
| 105 fMat[0] = m11; | |
| 106 fMat[1] = m12; | |
| 107 fMat[2] = m13; | |
| 108 fMat[3] = m21; | |
| 109 fMat[4] = m22; | |
| 110 fMat[5] = m23; | |
| 111 } | |
| 112 | |
| 113 /** Set the matrix to identity | |
| 114 */ | |
| 115 void reset() { | |
| 116 fMat[0] = fMat[4] = 1.0; | |
| 117 fMat[1] = fMat[3] = | |
| 118 fMat[2] = fMat[5] = 0.0; | |
| 119 } | |
| 120 | |
| 121 // alias for reset() | |
| 122 void setIdentity() { this->reset(); } | |
| 123 | |
| 124 DPoint mapPoint(const SkPoint& src) const { | |
| 125 DPoint pt = DPoint::Make(src.x(), src.y()); | |
| 126 return this->mapPoint(pt); | |
| 127 } | |
| 128 | |
| 129 DPoint mapPoint(const DPoint& src) const { | |
| 130 return DPoint::Make(fMat[0] * src.x() + fMat[1] * src.y() + fMat[2], | |
| 131 fMat[3] * src.x() + fMat[4] * src.y() + fMat[5]); | |
| 132 } | |
| 133 private: | |
| 134 double fMat[6]; | |
| 135 }; | |
| 136 | |
| 137 /////////////////////////////////////////////////////////////////////////////// | |
| 138 | |
| 139 static const double kClose = (SK_Scalar1 / 16.0); | |
| 140 static const double kCloseSqd = SkScalarMul(kClose, kClose); | |
| 141 static const double kNearlyZero = (SK_Scalar1 / (1 << 18)); | |
| 142 | |
| 143 static inline bool between_closed_open(double a, double b, double c, | |
| 144 double tolerance = 0.0, | |
| 145 bool xformToleranceToX = false) { | |
| 146 SkASSERT(tolerance >= 0.0); | |
| 147 double tolB = tolerance; | |
| 148 double tolC = tolerance; | |
| 149 | |
| 150 if (xformToleranceToX) { | |
| 151 // Canonical space is y = x^2 and the derivative of x^2 is 2x. | |
| 152 // So the slope of the tangent line at point (x, x^2) is 2x. | |
| 153 // | |
| 154 // /| | |
| 155 // sqrt(2x * 2x + 1 * 1) / | 2x | |
| 156 // /__| | |
| 157 // 1 | |
| 158 tolB = tolerance / sqrt(4.0 * b * b + 1.0); | |
| 159 tolC = tolerance / sqrt(4.0 * c * c + 1.0); | |
| 160 } | |
| 161 return b < c ? (a >= b - tolB && a < c - tolC) : | |
| 162 (a >= c - tolC && a < b - tolB); | |
| 163 } | |
| 164 | |
| 165 static inline bool between_closed(double a, double b, double c, | |
| 166 double tolerance = 0.0, | |
| 167 bool xformToleranceToX = false) { | |
| 168 SkASSERT(tolerance >= 0.0); | |
| 169 double tolB = tolerance; | |
| 170 double tolC = tolerance; | |
| 171 | |
| 172 if (xformToleranceToX) { | |
| 173 tolB = tolerance / sqrt(4.0 * b * b + 1.0); | |
| 174 tolC = tolerance / sqrt(4.0 * c * c + 1.0); | |
| 175 } | |
| 176 return b < c ? (a >= b - tolB && a <= c + tolC) : | |
| 177 (a >= c - tolC && a <= b + tolB); | |
| 178 } | |
| 179 | |
| 180 static inline bool nearly_zero(double x, double tolerance = kNearlyZero) { | |
| 181 SkASSERT(tolerance >= 0.0); | |
| 182 return fabs(x) <= tolerance; | |
| 183 } | |
| 184 | |
| 185 static inline bool nearly_equal(double x, double y, | |
| 186 double tolerance = kNearlyZero, | |
| 187 bool xformToleranceToX = false) { | |
| 188 SkASSERT(tolerance >= 0.0); | |
| 189 if (xformToleranceToX) { | |
| 190 tolerance = tolerance / sqrt(4.0 * y * y + 1.0); | |
| 191 } | |
| 192 return fabs(x - y) <= tolerance; | |
| 193 } | |
| 194 | |
| 195 static inline double sign_of(const double &val) { | |
| 196 return (val < 0.0) ? -1.0 : 1.0; | |
| 197 } | |
| 198 | |
| 199 static bool is_colinear(const SkPoint pts[3]) { | |
| 200 return nearly_zero((pts[1].y() - pts[0].y()) * (pts[1].x() - pts[2].x()) - | |
| 201 (pts[1].y() - pts[2].y()) * (pts[1].x() - pts[0].x()), kC
loseSqd); | |
| 202 } | |
| 203 | |
| 204 class PathSegment { | |
| 205 public: | |
| 206 enum { | |
| 207 // These enum values are assumed in member functions below. | |
| 208 kLine = 0, | |
| 209 kQuad = 1, | |
| 210 } fType; | |
| 211 | |
| 212 // line uses 2 pts, quad uses 3 pts | |
| 213 SkPoint fPts[3]; | |
| 214 | |
| 215 DPoint fP0T, fP2T; | |
| 216 DAffineMatrix fXformMatrix; | |
| 217 double fScalingFactor; | |
| 218 double fScalingFactorSqd; | |
| 219 double fNearlyZeroScaled; | |
| 220 SkRect fBoundingBox; | |
| 221 | |
| 222 void init(); | |
| 223 | |
| 224 int countPoints() { | |
| 225 GR_STATIC_ASSERT(0 == kLine && 1 == kQuad); | |
| 226 return fType + 2; | |
| 227 } | |
| 228 | |
| 229 const SkPoint& endPt() const { | |
| 230 GR_STATIC_ASSERT(0 == kLine && 1 == kQuad); | |
| 231 return fPts[fType + 1]; | |
| 232 } | |
| 233 }; | |
| 234 | |
| 235 typedef SkTArray<PathSegment, true> PathSegmentArray; | |
| 236 | |
| 237 void PathSegment::init() { | |
| 238 const DPoint p0 = DPoint::Make(fPts[0].x(), fPts[0].y()); | |
| 239 const DPoint p2 = DPoint::Make(this->endPt().x(), this->endPt().y()); | |
| 240 const double p0x = p0.x(); | |
| 241 const double p0y = p0.y(); | |
| 242 const double p2x = p2.x(); | |
| 243 const double p2y = p2.y(); | |
| 244 | |
| 245 fBoundingBox.set(fPts[0], this->endPt()); | |
| 246 | |
| 247 if (fType == PathSegment::kLine) { | |
| 248 fScalingFactorSqd = fScalingFactor = 1.0; | |
| 249 double hypotenuse = DPoint::Distance(p0, p2); | |
| 250 | |
| 251 const double cosTheta = (p2x - p0x) / hypotenuse; | |
| 252 const double sinTheta = (p2y - p0y) / hypotenuse; | |
| 253 | |
| 254 fXformMatrix.setAffine( | |
| 255 cosTheta, sinTheta, -(cosTheta * p0x) - (sinTheta * p0y), | |
| 256 -sinTheta, cosTheta, (sinTheta * p0x) - (cosTheta * p0y) | |
| 257 ); | |
| 258 } else { | |
| 259 SkASSERT(fType == PathSegment::kQuad); | |
| 260 | |
| 261 // Calculate bounding box | |
| 262 const SkPoint _P1mP0 = fPts[1] - fPts[0]; | |
| 263 SkPoint t = _P1mP0 - fPts[2] + fPts[1]; | |
| 264 t.fX = _P1mP0.x() / t.x(); | |
| 265 t.fY = _P1mP0.y() / t.y(); | |
| 266 t.fX = SkScalarClampMax(t.x(), 1.0); | |
| 267 t.fY = SkScalarClampMax(t.y(), 1.0); | |
| 268 t.fX = _P1mP0.x() * t.x(); | |
| 269 t.fY = _P1mP0.y() * t.y(); | |
| 270 const SkPoint m = fPts[0] + t; | |
| 271 fBoundingBox.growToInclude(&m, 1); | |
| 272 | |
| 273 const double p1x = fPts[1].x(); | |
| 274 const double p1y = fPts[1].y(); | |
| 275 | |
| 276 const double p0xSqd = p0x * p0x; | |
| 277 const double p0ySqd = p0y * p0y; | |
| 278 const double p2xSqd = p2x * p2x; | |
| 279 const double p2ySqd = p2y * p2y; | |
| 280 const double p1xSqd = p1x * p1x; | |
| 281 const double p1ySqd = p1y * p1y; | |
| 282 | |
| 283 const double p01xProd = p0x * p1x; | |
| 284 const double p02xProd = p0x * p2x; | |
| 285 const double b12xProd = p1x * p2x; | |
| 286 const double p01yProd = p0y * p1y; | |
| 287 const double p02yProd = p0y * p2y; | |
| 288 const double b12yProd = p1y * p2y; | |
| 289 | |
| 290 const double sqrtA = p0y - (2.0 * p1y) + p2y; | |
| 291 const double a = sqrtA * sqrtA; | |
| 292 const double h = -1.0 * (p0y - (2.0 * p1y) + p2y) * (p0x - (2.0 * p1x) +
p2x); | |
| 293 const double sqrtB = p0x - (2.0 * p1x) + p2x; | |
| 294 const double b = sqrtB * sqrtB; | |
| 295 const double c = (p0xSqd * p2ySqd) - (4.0 * p01xProd * b12yProd) | |
| 296 - (2.0 * p02xProd * p02yProd) + (4.0 * p02xProd * p1ySqd) | |
| 297 + (4.0 * p1xSqd * p02yProd) - (4.0 * b12xProd * p01yProd) | |
| 298 + (p2xSqd * p0ySqd); | |
| 299 const double g = (p0x * p02yProd) - (2.0 * p0x * p1ySqd) | |
| 300 + (2.0 * p0x * b12yProd) - (p0x * p2ySqd) | |
| 301 + (2.0 * p1x * p01yProd) - (4.0 * p1x * p02yProd) | |
| 302 + (2.0 * p1x * b12yProd) - (p2x * p0ySqd) | |
| 303 + (2.0 * p2x * p01yProd) + (p2x * p02yProd) | |
| 304 - (2.0 * p2x * p1ySqd); | |
| 305 const double f = -((p0xSqd * p2y) - (2.0 * p01xProd * p1y) | |
| 306 - (2.0 * p01xProd * p2y) - (p02xProd * p0y) | |
| 307 + (4.0 * p02xProd * p1y) - (p02xProd * p2y) | |
| 308 + (2.0 * p1xSqd * p0y) + (2.0 * p1xSqd * p2y) | |
| 309 - (2.0 * b12xProd * p0y) - (2.0 * b12xProd * p1y) | |
| 310 + (p2xSqd * p0y)); | |
| 311 | |
| 312 const double cosTheta = sqrt(a / (a + b)); | |
| 313 const double sinTheta = -1.0 * sign_of((a + b) * h) * sqrt(b / (a + b)); | |
| 314 | |
| 315 const double gDef = cosTheta * g - sinTheta * f; | |
| 316 const double fDef = sinTheta * g + cosTheta * f; | |
| 317 | |
| 318 | |
| 319 const double x0 = gDef / (a + b); | |
| 320 const double y0 = (1.0 / (2.0 * fDef)) * (c - (gDef * gDef / (a + b))); | |
| 321 | |
| 322 | |
| 323 const double lambda = -1.0 * ((a + b) / (2.0 * fDef)); | |
| 324 fScalingFactor = fabs(1.0 / lambda); | |
| 325 fScalingFactorSqd = fScalingFactor * fScalingFactor; | |
| 326 | |
| 327 const double lambda_cosTheta = lambda * cosTheta; | |
| 328 const double lambda_sinTheta = lambda * sinTheta; | |
| 329 | |
| 330 fXformMatrix.setAffine( | |
| 331 lambda_cosTheta, -lambda_sinTheta, lambda * x0, | |
| 332 lambda_sinTheta, lambda_cosTheta, lambda * y0 | |
| 333 ); | |
| 334 } | |
| 335 | |
| 336 fNearlyZeroScaled = kNearlyZero / fScalingFactor; | |
| 337 | |
| 338 fP0T = fXformMatrix.mapPoint(p0); | |
| 339 fP2T = fXformMatrix.mapPoint(p2); | |
| 340 } | |
| 341 | |
| 342 static void init_distances(DFData* data, int size) { | |
| 343 DFData* currData = data; | |
| 344 | |
| 345 for (int i = 0; i < size; ++i) { | |
| 346 // init distance to "far away" | |
| 347 currData->fDistSq = SK_DistanceFieldMagnitude * SK_DistanceFieldMagnitud
e; | |
| 348 currData->fDeltaWindingScore = 0; | |
| 349 ++currData; | |
| 350 } | |
| 351 } | |
| 352 | |
| 353 static inline void add_line_to_segment(const SkPoint pts[2], | |
| 354 PathSegmentArray* segments) { | |
| 355 segments->push_back(); | |
| 356 segments->back().fType = PathSegment::kLine; | |
| 357 segments->back().fPts[0] = pts[0]; | |
| 358 segments->back().fPts[1] = pts[1]; | |
| 359 | |
| 360 segments->back().init(); | |
| 361 } | |
| 362 | |
| 363 static inline void add_quad_segment(const SkPoint pts[3], | |
| 364 PathSegmentArray* segments) { | |
| 365 if (pts[0].distanceToSqd(pts[1]) < kCloseSqd || | |
| 366 pts[1].distanceToSqd(pts[2]) < kCloseSqd || | |
| 367 is_colinear(pts)) { | |
| 368 if (pts[0] != pts[2]) { | |
| 369 SkPoint line_pts[2]; | |
| 370 line_pts[0] = pts[0]; | |
| 371 line_pts[1] = pts[2]; | |
| 372 add_line_to_segment(line_pts, segments); | |
| 373 } | |
| 374 } else { | |
| 375 segments->push_back(); | |
| 376 segments->back().fType = PathSegment::kQuad; | |
| 377 segments->back().fPts[0] = pts[0]; | |
| 378 segments->back().fPts[1] = pts[1]; | |
| 379 segments->back().fPts[2] = pts[2]; | |
| 380 | |
| 381 segments->back().init(); | |
| 382 } | |
| 383 } | |
| 384 | |
| 385 static inline void add_cubic_segments(const SkPoint pts[4], | |
| 386 PathSegmentArray* segments) { | |
| 387 SkSTArray<15, SkPoint, true> quads; | |
| 388 GrPathUtils::convertCubicToQuads(pts, SK_Scalar1, &quads); | |
| 389 int count = quads.count(); | |
| 390 for (int q = 0; q < count; q += 3) { | |
| 391 add_quad_segment(&quads[q], segments); | |
| 392 } | |
| 393 } | |
| 394 | |
| 395 static float calculate_nearest_point_for_quad( | |
| 396 const PathSegment& segment, | |
| 397 const DPoint &xFormPt) { | |
| 398 static const float kThird = 0.33333333333f; | |
| 399 static const float kTwentySeventh = 0.037037037f; | |
| 400 | |
| 401 const float a = 0.5f - (float)xFormPt.y(); | |
| 402 const float b = -0.5f * (float)xFormPt.x(); | |
| 403 | |
| 404 const float a3 = a * a * a; | |
| 405 const float b2 = b * b; | |
| 406 | |
| 407 const float c = (b2 * 0.25f) + (a3 * kTwentySeventh); | |
| 408 | |
| 409 if (c >= 0.f) { | |
| 410 const float sqrtC = sqrt(c); | |
| 411 const float result = (float)cbrt((-b * 0.5f) + sqrtC) + (float)cbrt((-b
* 0.5f) - sqrtC); | |
| 412 return result; | |
| 413 } else { | |
| 414 const float cosPhi = (float)sqrt((b2 * 0.25f) * (-27.f / a3)) * ((b > 0)
? -1.f : 1.f); | |
| 415 const float phi = (float)acos(cosPhi); | |
| 416 float result; | |
| 417 if (xFormPt.x() > 0.f) { | |
| 418 result = 2.f * (float)sqrt(-a * kThird) * (float)cos(phi * kThird); | |
| 419 if (!between_closed(result, segment.fP0T.x(), segment.fP2T.x())) { | |
| 420 result = 2.f * (float)sqrt(-a * kThird) * (float)cos((phi * kThi
rd) + (SK_ScalarPI * 2.f * kThird)); | |
| 421 } | |
| 422 } else { | |
| 423 result = 2.f * (float)sqrt(-a * kThird) * (float)cos((phi * kThird)
+ (SK_ScalarPI * 2.f * kThird)); | |
| 424 if (!between_closed(result, segment.fP0T.x(), segment.fP2T.x())) { | |
| 425 result = 2.f * (float)sqrt(-a * kThird) * (float)cos(phi * kThir
d); | |
| 426 } | |
| 427 } | |
| 428 return result; | |
| 429 } | |
| 430 } | |
| 431 | |
| 432 // This structure contains some intermediate values shared by the same row. | |
| 433 // It is used to calculate segment side of a quadratic bezier. | |
| 434 struct RowData { | |
| 435 // The intersection type of a scanline and y = x * x parabola in canonical s
pace. | |
| 436 enum IntersectionType { | |
| 437 kNoIntersection, | |
| 438 kVerticalLine, | |
| 439 kTangentLine, | |
| 440 kTwoPointsIntersect | |
| 441 } fIntersectionType; | |
| 442 | |
| 443 // The direction of the quadratic segment/scanline in the canonical space. | |
| 444 // 1: The quadratic segment/scanline going from negative x-axis to positive
x-axis. | |
| 445 // 0: The scanline is a vertical line in the canonical space. | |
| 446 // -1: The quadratic segment/scanline going from positive x-axis to negative
x-axis. | |
| 447 int fQuadXDirection; | |
| 448 int fScanlineXDirection; | |
| 449 | |
| 450 // The y-value(equal to x*x) of intersection point for the kVerticalLine int
ersection type. | |
| 451 double fYAtIntersection; | |
| 452 | |
| 453 // The x-value for two intersection points. | |
| 454 double fXAtIntersection1; | |
| 455 double fXAtIntersection2; | |
| 456 }; | |
| 457 | |
| 458 void precomputation_for_row( | |
| 459 RowData *rowData, | |
| 460 const PathSegment& segment, | |
| 461 const SkPoint& pointLeft, | |
| 462 const SkPoint& pointRight | |
| 463 ) { | |
| 464 if (segment.fType != PathSegment::kQuad) { | |
| 465 return; | |
| 466 } | |
| 467 | |
| 468 const DPoint& xFormPtLeft = segment.fXformMatrix.mapPoint(pointLeft); | |
| 469 const DPoint& xFormPtRight = segment.fXformMatrix.mapPoint(pointRight);; | |
| 470 | |
| 471 rowData->fQuadXDirection = (int)sign_of(segment.fP2T.x() - segment.fP0T.x())
; | |
| 472 rowData->fScanlineXDirection = (int)sign_of(xFormPtRight.x() - xFormPtLeft.x
()); | |
| 473 | |
| 474 const double x1 = xFormPtLeft.x(); | |
| 475 const double y1 = xFormPtLeft.y(); | |
| 476 const double x2 = xFormPtRight.x(); | |
| 477 const double y2 = xFormPtRight.y(); | |
| 478 | |
| 479 if (nearly_equal(x1, x2)) { | |
| 480 rowData->fIntersectionType = RowData::kVerticalLine; | |
| 481 rowData->fYAtIntersection = x1 * x1; | |
| 482 rowData->fScanlineXDirection = 0; | |
| 483 return; | |
| 484 } | |
| 485 | |
| 486 // Line y = mx + b | |
| 487 const double m = (y2 - y1) / (x2 - x1); | |
| 488 const double b = -m * x1 + y1; | |
| 489 | |
| 490 const double c = m * m + 4.0 * b; | |
| 491 | |
| 492 if (nearly_zero(c, 4.0 * kNearlyZero * kNearlyZero)) { | |
| 493 rowData->fIntersectionType = RowData::kTangentLine; | |
| 494 rowData->fXAtIntersection1 = m / 2.0; | |
| 495 rowData->fXAtIntersection2 = m / 2.0; | |
| 496 } else if (c < 0.0) { | |
| 497 rowData->fIntersectionType = RowData::kNoIntersection; | |
| 498 return; | |
| 499 } else { | |
| 500 rowData->fIntersectionType = RowData::kTwoPointsIntersect; | |
| 501 const double d = sqrt(c); | |
| 502 rowData->fXAtIntersection1 = (m + d) / 2.0; | |
| 503 rowData->fXAtIntersection2 = (m - d) / 2.0; | |
| 504 } | |
| 505 } | |
| 506 | |
| 507 SegSide calculate_side_of_quad( | |
| 508 const PathSegment& segment, | |
| 509 const SkPoint& point, | |
| 510 const DPoint& xFormPt, | |
| 511 const RowData& rowData) { | |
| 512 SegSide side = kNA_SegSide; | |
| 513 | |
| 514 if (RowData::kVerticalLine == rowData.fIntersectionType) { | |
| 515 side = (SegSide)(int)(sign_of(rowData.fYAtIntersection - xFormPt.y()) *
rowData.fQuadXDirection); | |
| 516 } | |
| 517 else if (RowData::kTwoPointsIntersect == rowData.fIntersectionType) { | |
| 518 const double p1 = rowData.fXAtIntersection1; | |
| 519 const double p2 = rowData.fXAtIntersection2; | |
| 520 | |
| 521 int signP1 = (int)sign_of(p1 - xFormPt.x()); | |
| 522 bool includeP1 = true; | |
| 523 bool includeP2 = true; | |
| 524 | |
| 525 if ((nearly_equal(p1, segment.fP0T.x(), segment.fNearlyZeroScaled, true)
&& | |
| 526 rowData.fQuadXDirection * rowData.fScanlineXDirection == -1) || | |
| 527 (nearly_equal(p1, segment.fP2T.x(), segment.fNearlyZeroScaled, true)
&& | |
| 528 rowData.fQuadXDirection * rowData.fScanlineXDirection == 1)) { | |
| 529 includeP1 = false; | |
| 530 } | |
| 531 if ((nearly_equal(p2, segment.fP0T.x(), segment.fNearlyZeroScaled, true)
&& | |
| 532 rowData.fQuadXDirection * rowData.fScanlineXDirection == 1) || | |
| 533 (nearly_equal(p2, segment.fP2T.x(), segment.fNearlyZeroScaled, true)
&& | |
| 534 rowData.fQuadXDirection * rowData.fScanlineXDirection == -1)) { | |
| 535 includeP2 = false; | |
| 536 } | |
| 537 | |
| 538 if (includeP1 && between_closed(p1, segment.fP0T.x(), segment.fP2T.x(), | |
| 539 segment.fNearlyZeroScaled, true)) { | |
| 540 side = (SegSide)((-signP1) * rowData.fQuadXDirection); | |
| 541 } | |
| 542 if (includeP2 && between_closed(p2, segment.fP0T.x(), segment.fP2T.x(), | |
| 543 segment.fNearlyZeroScaled, true)) { | |
| 544 int signP2 = (int)sign_of(p2 - xFormPt.x()); | |
| 545 if (side == kNA_SegSide || signP2 == 1) { | |
| 546 side = (SegSide)(signP2 * rowData.fQuadXDirection); | |
| 547 } | |
| 548 } | |
| 549 } else if (RowData::kTangentLine == rowData.fIntersectionType) { | |
| 550 // The scanline is the tangent line of current quadratic segment. | |
| 551 | |
| 552 const double p = rowData.fXAtIntersection1; | |
| 553 int signP = (int)sign_of(p - xFormPt.x()); | |
| 554 if (rowData.fScanlineXDirection == 1 && | |
| 555 // The path start or end at the tangent point. | |
| 556 (nearly_equal(p, segment.fP0T.x(), segment.fNearlyZeroScaled, true)
|| | |
| 557 nearly_equal(p, segment.fP2T.x(), segment.fNearlyZeroScaled, true))
) { | |
| 558 side = (SegSide)(signP * rowData.fQuadXDirection); | |
| 559 } | |
| 560 } | |
| 561 | |
| 562 return side; | |
| 563 } | |
| 564 | |
| 565 static float distance_to_segment(const SkPoint& point, | |
| 566 const PathSegment& segment, | |
| 567 const RowData& rowData, | |
| 568 SegSide* side) { | |
| 569 SkASSERT(side); | |
| 570 | |
| 571 const DPoint xformPt = segment.fXformMatrix.mapPoint(point); | |
| 572 | |
| 573 if (segment.fType == PathSegment::kLine) { | |
| 574 float result = SK_DistanceFieldPad * SK_DistanceFieldPad; | |
| 575 | |
| 576 if (between_closed(xformPt.x(), segment.fP0T.x(), segment.fP2T.x())) { | |
| 577 result = (float)(xformPt.y() * xformPt.y()); | |
| 578 } else if (xformPt.x() < segment.fP0T.x()) { | |
| 579 result = (float)(xformPt.x() * xformPt.x() + xformPt.y() * xformPt.y
()); | |
| 580 } else { | |
| 581 result = (float)((xformPt.x() - segment.fP2T.x()) * (xformPt.x() - s
egment.fP2T.x()) | |
| 582 + xformPt.y() * xformPt.y()); | |
| 583 } | |
| 584 | |
| 585 if (between_closed_open(point.y(), segment.fBoundingBox.top(), | |
| 586 segment.fBoundingBox.bottom())) { | |
| 587 *side = (SegSide)(int)sign_of(-xformPt.y()); | |
| 588 } else { | |
| 589 *side = kNA_SegSide; | |
| 590 } | |
| 591 return result; | |
| 592 } else { | |
| 593 SkASSERT(segment.fType == PathSegment::kQuad); | |
| 594 | |
| 595 const float nearestPoint = calculate_nearest_point_for_quad(segment, xfo
rmPt); | |
| 596 | |
| 597 float dist; | |
| 598 | |
| 599 if (between_closed(nearestPoint, segment.fP0T.x(), segment.fP2T.x())) { | |
| 600 DPoint x = DPoint::Make(nearestPoint, nearestPoint * nearestPoint); | |
| 601 dist = (float)xformPt.distanceToSqd(x); | |
| 602 } else { | |
| 603 const float distToB0T = (float)xformPt.distanceToSqd(segment.fP0T); | |
| 604 const float distToB2T = (float)xformPt.distanceToSqd(segment.fP2T); | |
| 605 | |
| 606 if (distToB0T < distToB2T) { | |
| 607 dist = distToB0T; | |
| 608 } else { | |
| 609 dist = distToB2T; | |
| 610 } | |
| 611 } | |
| 612 | |
| 613 if (between_closed_open(point.y(), segment.fBoundingBox.top(), | |
| 614 segment.fBoundingBox.bottom())) { | |
| 615 *side = calculate_side_of_quad(segment, point, xformPt, rowData); | |
| 616 } else { | |
| 617 *side = kNA_SegSide; | |
| 618 } | |
| 619 | |
| 620 return (float)(dist * segment.fScalingFactorSqd); | |
| 621 } | |
| 622 } | |
| 623 | |
| 624 static void calculate_distance_field_data(PathSegmentArray* segments, | |
| 625 DFData* dataPtr, | |
| 626 int width, int height) { | |
| 627 int count = segments->count(); | |
| 628 for (int a = 0; a < count; ++a) { | |
| 629 PathSegment& segment = (*segments)[a]; | |
| 630 const SkRect& segBB = segment.fBoundingBox.makeOutset( | |
| 631 SK_DistanceFieldPad, SK_DistanceFieldPad); | |
| 632 int startColumn = (int)segBB.left(); | |
| 633 int endColumn = SkScalarCeilToInt(segBB.right()); | |
| 634 | |
| 635 int startRow = (int)segBB.top(); | |
| 636 int endRow = SkScalarCeilToInt(segBB.bottom()); | |
| 637 | |
| 638 SkASSERT((startColumn >= 0) && "StartColumn < 0!"); | |
| 639 SkASSERT((endColumn <= width) && "endColumn > width!"); | |
| 640 SkASSERT((startRow >= 0) && "StartRow < 0!"); | |
| 641 SkASSERT((endRow <= height) && "EndRow > height!"); | |
| 642 | |
| 643 for (int row = startRow; row < endRow; ++row) { | |
| 644 SegSide prevSide = kNA_SegSide; | |
| 645 const float pY = row + 0.5f; | |
| 646 RowData rowData; | |
| 647 | |
| 648 const SkPoint pointLeft = SkPoint::Make((SkScalar)startColumn, pY); | |
| 649 const SkPoint pointRight = SkPoint::Make((SkScalar)endColumn, pY); | |
| 650 | |
| 651 precomputation_for_row(&rowData, segment, pointLeft, pointRight); | |
| 652 | |
| 653 for (int col = startColumn; col < endColumn; ++col) { | |
| 654 int idx = (row * width) + col; | |
| 655 | |
| 656 const float pX = col + 0.5f; | |
| 657 const SkPoint point = SkPoint::Make(pX, pY); | |
| 658 | |
| 659 const float distSq = dataPtr[idx].fDistSq; | |
| 660 int dilation = distSq < 1.5 * 1.5 ? 1 : | |
| 661 distSq < 2.5 * 2.5 ? 2 : | |
| 662 distSq < 3.5 * 3.5 ? 3 : SK_DistanceFieldPad; | |
| 663 if (dilation > SK_DistanceFieldPad) { | |
| 664 dilation = SK_DistanceFieldPad; | |
| 665 } | |
| 666 | |
| 667 // Optimisation for not calculating some points. | |
| 668 if (dilation != SK_DistanceFieldPad && !segment.fBoundingBox.rou
ndOut() | |
| 669 .makeOutset(dilation, dilation).contains(col, row)) { | |
| 670 continue; | |
| 671 } | |
| 672 | |
| 673 SegSide side = kNA_SegSide; | |
| 674 int deltaWindingScore = 0; | |
| 675 float currDistSq = distance_to_segment(point, segment, rowData
, &side); | |
| 676 if (prevSide == kLeft_SegSide && side == kRight_SegSide) { | |
| 677 deltaWindingScore = -1; | |
| 678 } else if (prevSide == kRight_SegSide && side == kLeft_SegSide)
{ | |
| 679 deltaWindingScore = 1; | |
| 680 } | |
| 681 | |
| 682 prevSide = side; | |
| 683 | |
| 684 if (currDistSq < distSq) { | |
| 685 dataPtr[idx].fDistSq = currDistSq; | |
| 686 } | |
| 687 | |
| 688 dataPtr[idx].fDeltaWindingScore += deltaWindingScore; | |
| 689 } | |
| 690 } | |
| 691 } | |
| 692 } | |
| 693 | |
| 694 template <int distanceMagnitude> | |
| 695 static unsigned char pack_distance_field_val(float dist) { | |
| 696 // The distance field is constructed as unsigned char values, so that the ze
ro value is at 128, | |
| 697 // Beside 128, we have 128 values in range [0, 128), but only 127 values in
range (128, 255]. | |
| 698 // So we multiply distanceMagnitude by 127/128 at the latter range to avoid
overflow. | |
| 699 dist = SkScalarPin(-dist, -distanceMagnitude, distanceMagnitude * 127.0f / 1
28.0f); | |
| 700 | |
| 701 // Scale into the positive range for unsigned distance. | |
| 702 dist += distanceMagnitude; | |
| 703 | |
| 704 // Scale into unsigned char range. | |
| 705 // Round to place negative and positive values as equally as possible around
128 | |
| 706 // (which represents zero). | |
| 707 return (unsigned char)SkScalarRoundToInt(dist / (2 * distanceMagnitude) * 25
6.0f); | |
| 708 } | |
| 709 | |
| 710 bool GrGenerateDistanceFieldFromPath(unsigned char* distanceField, | |
| 711 const SkPath& path, const SkMatrix& drawMat
rix, | |
| 712 int width, int height, size_t rowBytes) { | |
| 713 SkASSERT(distanceField); | |
| 714 | |
| 715 SkPath simplifiedPath; | |
| 716 SkPath workingPath; | |
| 717 if (Simplify(path, &simplifiedPath)) { | |
| 718 workingPath = simplifiedPath; | |
| 719 } else { | |
| 720 workingPath = path; | |
| 721 } | |
| 722 | |
| 723 if (!IsDistanceFieldSupportedFillType(workingPath.getFillType())) { | |
| 724 return false; | |
| 725 } | |
| 726 | |
| 727 SkMatrix m = drawMatrix; | |
| 728 m.postTranslate(SK_DistanceFieldPad, SK_DistanceFieldPad); | |
| 729 workingPath.transform(m); | |
| 730 | |
| 731 // create temp data | |
| 732 size_t dataSize = width * height * sizeof(DFData); | |
| 733 SkAutoSMalloc<1024> dfStorage(dataSize); | |
| 734 DFData* dataPtr = (DFData*) dfStorage.get(); | |
| 735 | |
| 736 // create initial distance data | |
| 737 init_distances(dataPtr, width * height); | |
| 738 | |
| 739 SkPath::Iter iter(workingPath, true); | |
| 740 SkSTArray<15, PathSegment, true> segments; | |
| 741 | |
| 742 for (;;) { | |
| 743 SkPoint pts[4]; | |
| 744 SkPath::Verb verb = iter.next(pts); | |
| 745 switch (verb) { | |
| 746 case SkPath::kMove_Verb: | |
| 747 break; | |
| 748 case SkPath::kLine_Verb: { | |
| 749 add_line_to_segment(pts, &segments); | |
| 750 break; | |
| 751 } | |
| 752 case SkPath::kQuad_Verb: | |
| 753 add_quad_segment(pts, &segments); | |
| 754 break; | |
| 755 case SkPath::kConic_Verb: { | |
| 756 SkScalar weight = iter.conicWeight(); | |
| 757 SkAutoConicToQuads converter; | |
| 758 const SkPoint* quadPts = converter.computeQuads(pts, weight, 0.5
f); | |
| 759 for (int i = 0; i < converter.countQuads(); ++i) { | |
| 760 add_quad_segment(quadPts + 2*i, &segments); | |
| 761 } | |
| 762 break; | |
| 763 } | |
| 764 case SkPath::kCubic_Verb: { | |
| 765 add_cubic_segments(pts, &segments); | |
| 766 break; | |
| 767 }; | |
| 768 default: | |
| 769 break; | |
| 770 } | |
| 771 if (verb == SkPath::kDone_Verb) { | |
| 772 break; | |
| 773 } | |
| 774 } | |
| 775 | |
| 776 calculate_distance_field_data(&segments, dataPtr, width, height); | |
| 777 | |
| 778 for (int row = 0; row < height; ++row) { | |
| 779 int windingNumber = 0; // Winding number start from zero for each scanli
ne | |
| 780 for (int col = 0; col < width; ++col) { | |
| 781 int idx = (row * width) + col; | |
| 782 windingNumber += dataPtr[idx].fDeltaWindingScore; | |
| 783 | |
| 784 enum DFSign { | |
| 785 kInside = -1, | |
| 786 kOutside = 1 | |
| 787 } dfSign; | |
| 788 | |
| 789 if (workingPath.getFillType() == SkPath::kWinding_FillType) { | |
| 790 dfSign = windingNumber ? kInside : kOutside; | |
| 791 } else if (workingPath.getFillType() == SkPath::kInverseWinding_Fill
Type) { | |
| 792 dfSign = windingNumber ? kOutside : kInside; | |
| 793 } else if (workingPath.getFillType() == SkPath::kEvenOdd_FillType) { | |
| 794 dfSign = (windingNumber % 2) ? kInside : kOutside; | |
| 795 } else { | |
| 796 SkASSERT(workingPath.getFillType() == SkPath::kInverseEvenOdd_Fi
llType); | |
| 797 dfSign = (windingNumber % 2) ? kOutside : kInside; | |
| 798 } | |
| 799 | |
| 800 // The winding number at the end of a scanline should be zero. | |
| 801 // SkASSERT(((col != width - 1) || (windingNumber == 0)) && | |
| 802 // "Winding number should be zero at the end of a scan line.
"); | |
| 803 // Fallback to use SkPath::contains to determine the sign of pixel i
nstead of assertion. | |
| 804 if (col == width - 1 && windingNumber != 0) { | |
| 805 for (int col = 0; col < width; ++col) { | |
| 806 int idx = (row * width) + col; | |
| 807 dfSign = workingPath.contains(col + 0.5, row + 0.5) ? kInsid
e : kOutside; | |
| 808 const float miniDist = sqrt(dataPtr[idx].fDistSq); | |
| 809 const float dist = dfSign * miniDist; | |
| 810 | |
| 811 unsigned char pixelVal = pack_distance_field_val<SK_Distance
FieldMagnitude>(dist); | |
| 812 | |
| 813 distanceField[(row * rowBytes) + col] = pixelVal; | |
| 814 } | |
| 815 continue; | |
| 816 } | |
| 817 | |
| 818 const float miniDist = sqrt(dataPtr[idx].fDistSq); | |
| 819 const float dist = dfSign * miniDist; | |
| 820 | |
| 821 unsigned char pixelVal = pack_distance_field_val<SK_DistanceFieldMag
nitude>(dist); | |
| 822 | |
| 823 distanceField[(row * rowBytes) + col] = pixelVal; | |
| 824 } | |
| 825 } | |
| 826 return true; | |
| 827 } | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2447403002:
Revert of Generate Signed Distance Field directly from vector path (Closed)
Base URL: https://skia.googlesource.com/skia.git@master