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Implement a first crude version of Curve.isSufficientlyFlat()

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Jürg Lehni 2011-06-04 12:40:36 +01:00
parent 5581eefd0c
commit bff3e14155
1 changed files with 37 additions and 0 deletions
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37
src/path/Curve.js
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@ -527,6 +527,43 @@ var Curve = this.Curve = Base.extend({
[p1x, p1y, p3x, p3y, p6x, p6y, p8x, p8y], // left
[p8x, p8y, p7x, p7y, p5x, p5y, p2x, p2y] // right
];
},
isSufficientlyFlat: function(p1x, p1y, c1x, c1y, c2x, c2y, p2x, p2y) {
// Inspired by Skia, but to be tested:
// Calculate 1/3 (m1) and 2/3 (m2) along the line between start
// (p1) and end (p2), measure distance from there the control
// points and see if they are further away than 1/2.
// Seems all very inaccurate, especially since the distance
// measurement is just the bigger one of x / y...
// TODO: Find a more accurate and still fast way to determine
// this.
var vx = (p2x - p1x) / 3,
vy = (p2y - p1y) / 3,
m1x = p1x + vx,
m1y = p1y + vy,
m2x = p2x - vx,
m2y = p2y - vy;
return Math.max(
Math.abs(m1x - c1x), Math.abs(m1y - c1y),
Math.abs(m2x - c1x), Math.abs(m1y - c1y)) < 1 / 2;
/*
// Thanks to Kaspar Fischer for the following:
// http://www.inf.ethz.ch/personal/fischerk/pubs/bez.pdf
var ux = 3 * c1x - 2 * p1x - p2x;
ux *= ux;
var uy = 3 * c1y - 2 * p1y - p2y;
uy *= uy;
var vx = 3 * c2x - 2 * p2x - p1x;
vx *= vx;
var vy = 3 * c2y - 2 * p2y - p1y;
vy *= vy;
if (ux < vx)
ux = vx;
if (uy < vy)
uy = vy;
return ux + uy <= 16 * Numerical.TOLERNACE * Numerical.TOLERNACE; // tolerance is 16 * tol ^ 2
*/
}
}
};