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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 "SkPathOpsCubic.h"
#include "SkPathOpsLine.h"
#include "SkPathOpsQuad.h"
// Sources
// computer-aided design - volume 22 number 9 november 1990 pp 538 - 549
// online at http://cagd.cs.byu.edu/~tom/papers/bezclip.pdf
// This turns a line segment into a parameterized line, of the form
// ax + by + c = 0
// When a^2 + b^2 == 1, the line is normalized.
// The distance to the line for (x, y) is d(x,y) = ax + by + c
//
// Note that the distances below are not necessarily normalized. To get the true
// distance, it's necessary to either call normalize() after xxxEndPoints(), or
// divide the result of xxxDistance() by sqrt(normalSquared())
class SkLineParameters {
public:
void cubicEndPoints(const SkDCubic& pts) {
cubicEndPoints(pts, 0, 1);
if (dx() == 0 && dy() == 0) {
cubicEndPoints(pts, 0, 2);
if (dx() == 0 && dy() == 0) {
cubicEndPoints(pts, 0, 3);
}
}
}
void cubicEndPoints(const SkDCubic& pts, int s, int e) {
a = pts[s].fY - pts[e].fY;
b = pts[e].fX - pts[s].fX;
c = pts[s].fX * pts[e].fY - pts[e].fX * pts[s].fY;
}
void lineEndPoints(const SkDLine& pts) {
a = pts[0].fY - pts[1].fY;
b = pts[1].fX - pts[0].fX;
c = pts[0].fX * pts[1].fY - pts[1].fX * pts[0].fY;
}
void quadEndPoints(const SkDQuad& pts) {
quadEndPoints(pts, 0, 1);
if (dx() == 0 && dy() == 0) {
quadEndPoints(pts, 0, 2);
}
}
void quadEndPoints(const SkDQuad& pts, int s, int e) {
a = pts[s].fY - pts[e].fY;
b = pts[e].fX - pts[s].fX;
c = pts[s].fX * pts[e].fY - pts[e].fX * pts[s].fY;
}
double normalSquared() const {
return a * a + b * b;
}
bool normalize() {
double normal = sqrt(normalSquared());
if (approximately_zero(normal)) {
a = b = c = 0;
return false;
}
double reciprocal = 1 / normal;
a *= reciprocal;
b *= reciprocal;
c *= reciprocal;
return true;
}
void cubicDistanceY(const SkDCubic& pts, SkDCubic& distance) const {
double oneThird = 1 / 3.0;
for (int index = 0; index < 4; ++index) {
distance[index].fX = index * oneThird;
distance[index].fY = a * pts[index].fX + b * pts[index].fY + c;
}
}
void quadDistanceY(const SkDQuad& pts, SkDQuad& distance) const {
double oneHalf = 1 / 2.0;
for (int index = 0; index < 3; ++index) {
distance[index].fX = index * oneHalf;
distance[index].fY = a * pts[index].fX + b * pts[index].fY + c;
}
}
double controlPtDistance(const SkDCubic& pts, int index) const {
SkASSERT(index == 1 || index == 2);
return a * pts[index].fX + b * pts[index].fY + c;
}
double controlPtDistance(const SkDQuad& pts) const {
return a * pts[1].fX + b * pts[1].fY + c;
}
double pointDistance(const SkDPoint& pt) const {
return a * pt.fX + b * pt.fY + c;
}
double dx() const {
return b;
}
double dy() const {
return -a;
}
private:
double a;
double b;
double c;
};
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