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gems: utility for calculating bezier curves

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Norman Feske 2017-07-28 16:27:46 +02:00 committed by Christian Helmuth
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/*
* \brief Utilities for calculating bezier curves
* \date 2017-07-28
* \author Norman Feske
*/
/*
* Copyright (C) 2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__GEMS__BEZIER_H_
#define _INCLUDE__GEMS__BEZIER_H_
/**
* Calculate quadratic bezier curve
*
* \param draw_line functor to be called to draw a line segment
* \param levels number of sub divisions
*
* The coordinates are specified in clock-wise order with point 1 being
* the start and point 3 the end of the curve.
*/
template <typename FUNC>
static inline void bezier(long x1, long y1, long x2, long y2, long x3, long y3,
FUNC const &draw_line, unsigned levels)
{
if (levels-- == 0) {
draw_line(x1, y1, x3, y3);
return;
}
long const x12 = (x1 + x2) / 2, y12 = (y1 + y2) / 2,
x23 = (x2 + x3) / 2, y23 = (y2 + y3) / 2,
x123 = (x12 + x23) / 2, y123 = (y12 + y23) / 2;
bezier(x1, y1, x12, y12, x123, y123, draw_line, levels);
bezier(x123, y123, x23, y23, x3, y3, draw_line, levels);
}
/**
* Calculate cubic bezier curve
*
* The arguments correspond to those of the quadratic version but with point 4
* being the end of the curve.
*/
template <typename FUNC>
static inline void bezier(long x1, long y1, long x2, long y2,
long x3, long y3, long x4, long y4,
FUNC const &draw_line, unsigned levels)
{
if (levels-- == 0) {
draw_line(x1, y1, x4, y4);
return;
}
long const x12 = (x1 + x2) / 2, y12 = (y1 + y2) / 2,
x23 = (x2 + x3) / 2, y23 = (y2 + y3) / 2,
x34 = (x3 + x4) / 2, y34 = (y3 + y4) / 2,
x123 = (x12 + x23) / 2, y123 = (y12 + y23) / 2,
x234 = (x23 + x34) / 2, y234 = (y23 + y34) / 2,
x1234 = (x123 + x234) / 2, y1234 = (y123 + y234) / 2;
bezier(x1, y1, x12, y12, x123, y123, x1234, y1234, draw_line, levels);
bezier(x1234, y1234, x234, y234, x34, y34, x4, y4, draw_line, levels);
}
#endif /* _INCLUDE__GEMS__BEZIER_H_ */