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/*
* 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 "SkPathOpsLine.h"
// may have this below somewhere else already:
// copying here because I thought it was clever
// Copyright 2001, softSurfer (www.softsurfer.com)
// This code may be freely used and modified for any purpose
// providing that this copyright notice is included with it.
// SoftSurfer makes no warranty for this code, and cannot be held
// liable for any real or imagined damage resulting from its use.
// Users of this code must verify correctness for their application.
// Assume that a class is already given for the object:
// Point with coordinates {float x, y;}
//===================================================================
// (only used by testing)
// isLeft(): tests if a point is Left|On|Right of an infinite line.
// Input: three points P0, P1, and P2
// Return: >0 for P2 left of the line through P0 and P1
// =0 for P2 on the line
// <0 for P2 right of the line
// See: the January 2001 Algorithm on Area of Triangles
// return (float) ((P1.x - P0.x)*(P2.y - P0.y) - (P2.x - P0.x)*(P1.y - P0.y));
double SkDLine::isLeft(const SkDPoint& pt) const {
SkDVector p0 = fPts[1] - fPts[0];
SkDVector p2 = pt - fPts[0];
return p0.cross(p2);
}
SkDPoint SkDLine::ptAtT(double t) const {
if (0 == t) {
return fPts[0];
}
if (1 == t) {
return fPts[1];
}
double one_t = 1 - t;
SkDPoint result = { one_t * fPts[0].fX + t * fPts[1].fX, one_t * fPts[0].fY + t * fPts[1].fY };
return result;
}
double SkDLine::exactPoint(const SkDPoint& xy) const {
if (xy == fPts[0]) { // do cheapest test first
return 0;
}
if (xy == fPts[1]) {
return 1;
}
return -1;
}
double SkDLine::nearPoint(const SkDPoint& xy, bool* unequal) const {
if (!AlmostBetweenUlps(fPts[0].fX, xy.fX, fPts[1].fX)
|| !AlmostBetweenUlps(fPts[0].fY, xy.fY, fPts[1].fY)) {
return -1;
}
// project a perpendicular ray from the point to the line; find the T on the line
SkDVector len = fPts[1] - fPts[0]; // the x/y magnitudes of the line
double denom = len.fX * len.fX + len.fY * len.fY; // see DLine intersectRay
SkDVector ab0 = xy - fPts[0];
double numer = len.fX * ab0.fX + ab0.fY * len.fY;
if (!between(0, numer, denom)) {
return -1;
}
double t = numer / denom;
SkDPoint realPt = ptAtT(t);
double dist = realPt.distance(xy); // OPTIMIZATION: can we compare against distSq instead ?
// find the ordinal in the original line with the largest unsigned exponent
double tiniest = SkTMin(SkTMin(SkTMin(fPts[0].fX, fPts[0].fY), fPts[1].fX), fPts[1].fY);
double largest = SkTMax(SkTMax(SkTMax(fPts[0].fX, fPts[0].fY), fPts[1].fX), fPts[1].fY);
largest = SkTMax(largest, -tiniest);
if (!AlmostEqualUlps(largest, largest + dist)) { // is the dist within ULPS tolerance?
return -1;
}
if (unequal) {
*unequal = (float) largest != (float) (largest + dist);
}
t = SkPinT(t); // a looser pin breaks skpwww_lptemp_com_3
SkASSERT(between(0, t, 1));
return t;
}
bool SkDLine::nearRay(const SkDPoint& xy) const {
// project a perpendicular ray from the point to the line; find the T on the line
SkDVector len = fPts[1] - fPts[0]; // the x/y magnitudes of the line
double denom = len.fX * len.fX + len.fY * len.fY; // see DLine intersectRay
SkDVector ab0 = xy - fPts[0];
double numer = len.fX * ab0.fX + ab0.fY * len.fY;
double t = numer / denom;
SkDPoint realPt = ptAtT(t);
double dist = realPt.distance(xy); // OPTIMIZATION: can we compare against distSq instead ?
// find the ordinal in the original line with the largest unsigned exponent
double tiniest = SkTMin(SkTMin(SkTMin(fPts[0].fX, fPts[0].fY), fPts[1].fX), fPts[1].fY);
double largest = SkTMax(SkTMax(SkTMax(fPts[0].fX, fPts[0].fY), fPts[1].fX), fPts[1].fY);
largest = SkTMax(largest, -tiniest);
return RoughlyEqualUlps(largest, largest + dist); // is the dist within ULPS tolerance?
}
double SkDLine::ExactPointH(const SkDPoint& xy, double left, double right, double y) {
if (xy.fY == y) {
if (xy.fX == left) {
return 0;
}
if (xy.fX == right) {
return 1;
}
}
return -1;
}
double SkDLine::NearPointH(const SkDPoint& xy, double left, double right, double y) {
if (!AlmostBequalUlps(xy.fY, y)) {
return -1;
}
if (!AlmostBetweenUlps(left, xy.fX, right)) {
return -1;
}
double t = (xy.fX - left) / (right - left);
t = SkPinT(t);
SkASSERT(between(0, t, 1));
double realPtX = (1 - t) * left + t * right;
SkDVector distU = {xy.fY - y, xy.fX - realPtX};
double distSq = distU.fX * distU.fX + distU.fY * distU.fY;
double dist = sqrt(distSq); // OPTIMIZATION: can we compare against distSq instead ?
double tiniest = SkTMin(SkTMin(y, left), right);
double largest = SkTMax(SkTMax(y, left), right);
largest = SkTMax(largest, -tiniest);
if (!AlmostEqualUlps(largest, largest + dist)) { // is the dist within ULPS tolerance?
return -1;
}
return t;
}
double SkDLine::ExactPointV(const SkDPoint& xy, double top, double bottom, double x) {
if (xy.fX == x) {
if (xy.fY == top) {
return 0;
}
if (xy.fY == bottom) {
return 1;
}
}
return -1;
}
double SkDLine::NearPointV(const SkDPoint& xy, double top, double bottom, double x) {
if (!AlmostBequalUlps(xy.fX, x)) {
return -1;
}
if (!AlmostBetweenUlps(top, xy.fY, bottom)) {
return -1;
}
double t = (xy.fY - top) / (bottom - top);
t = SkPinT(t);
SkASSERT(between(0, t, 1));
double realPtY = (1 - t) * top + t * bottom;
SkDVector distU = {xy.fX - x, xy.fY - realPtY};
double distSq = distU.fX * distU.fX + distU.fY * distU.fY;
double dist = sqrt(distSq); // OPTIMIZATION: can we compare against distSq instead ?
double tiniest = SkTMin(SkTMin(x, top), bottom);
double largest = SkTMax(SkTMax(x, top), bottom);
largest = SkTMax(largest, -tiniest);
if (!AlmostEqualUlps(largest, largest + dist)) { // is the dist within ULPS tolerance?
return -1;
}
return t;
}
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