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