skia / skia / fb35940de79fd67f8739601bebdd3d75089b1522 / . / experimental / Intersection / LineParameterization.cpp

/* | |

* Copyright 2012 Google Inc. | |

* | |

* Use of this source code is governed by a BSD-style license that can be | |

* found in the LICENSE file. | |

*/ | |

#include "CurveIntersection.h" | |

/* This rejects coincidence with two muls, two adds, and one cmp. | |

Coincident candidates will take another four muls and two adds, but may still | |

fail if they don't overlap. (The overlap test isn't performed here.) | |

*/ | |

bool implicit_matches(const _Line& one, const _Line& two) { | |

_Point oneD, twoD; | |

tangent(one, oneD); | |

tangent(two, twoD); | |

/* See if the slopes match, i.e. | |

dx1 / dy1 == dx2 / dy2 | |

(dy1 * dy2) * dx1 / dy1 == (dy1 * dy2) * dx2 / dy2 | |

dy2 * dx1 == dy1 * dx2 | |

*/ | |

if (!AlmostEqualUlps(oneD.x * twoD.y, twoD.x * oneD.y)) { | |

return false; | |

} | |

/* See if the axis intercepts match, i.e. | |

y0 - x0 * dy / dx == y1 - x1 * dy / dx | |

dx * (y0 - x0 * dy / dx) == dx * (y1 - x1 * dy / dx) | |

dx * y0 - x0 * dy == dx * y1 - x1 * dy | |

*/ | |

if (!AlmostEqualUlps(oneD.x * one[0].y - oneD.y * one[0].x, | |

oneD.x * two[0].y - oneD.y * two[0].x)) { | |

return false; | |

} | |

return true; | |

} | |

bool implicit_matches_ulps(const _Line& one, const _Line& two, int ulps) { | |

_Point oneD, twoD; | |

tangent(one, oneD); | |

tangent(two, twoD); | |

/* See if the slopes match, i.e. | |

dx1 / dy1 == dx2 / dy2 | |

(dy1 * dy2) * dx1 / dy1 == (dy1 * dy2) * dx2 / dy2 | |

dy2 * dx1 == dy1 * dx2 | |

*/ | |

int diff = UlpsDiff((float) (oneD.x * twoD.y), (float) (twoD.x * oneD.y)); | |

if (diff < 0 || diff > ulps) { | |

return false; | |

} | |

/* See if the axis intercepts match, i.e. | |

y0 - x0 * dy / dx == y1 - x1 * dy / dx | |

dx * (y0 - x0 * dy / dx) == dx * (y1 - x1 * dy / dx) | |

dx * y0 - x0 * dy == dx * y1 - x1 * dy | |

*/ | |

diff = UlpsDiff((float) (oneD.x * one[0].y - oneD.y * one[0].x), | |

(float) (oneD.x * two[0].y - oneD.y * two[0].x)); | |

return diff >= 0 && diff <= ulps; | |

} | |

void tangent(const _Line& line, _Point& result) { | |

result.x = line[0].x - line[1].x; | |

result.y = line[0].y - line[1].y; | |

} |