210 lines
5.8 KiB
C++
210 lines
5.8 KiB
C++
//----------------------------------------------------------------------------
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// Anti-Grain Geometry - Version 2.2
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// Copyright (C) 2002-2004 Maxim Shemanarev (http://www.antigrain.com)
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//
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// Permission to copy, use, modify, sell and distribute this software
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// is granted provided this copyright notice appears in all copies.
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// This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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//
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//----------------------------------------------------------------------------
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// Contact: mcseem@antigrain.com
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// mcseemagg@yahoo.com
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// http://www.antigrain.com
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//----------------------------------------------------------------------------
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//
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// Liang-Barsky clipping
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//
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//----------------------------------------------------------------------------
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#ifndef AGG_CLIP_LIANG_BARSKY_INCLUDED
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#define AGG_CLIP_LIANG_BARSKY_INCLUDED
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#include "agg_basics.h"
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namespace agg
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{
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//----------------------------------------------------------clipping_flags
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// Determine the clipping code of the vertex according to the
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// Cyrus-Beck line clipping algorithm
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//
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// | |
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// 0110 | 0010 | 0011
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// | |
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// -------+--------+-------- clip_box.y2
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// | |
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// 0100 | 0000 | 0001
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// | |
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// -------+--------+-------- clip_box.y1
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// | |
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// 1100 | 1000 | 1001
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// | |
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// clip_box.x1 clip_box.x2
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//
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//
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template<class T>
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inline unsigned clipping_flags(T x, T y, const rect_base<T>& clip_box)
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{
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return (x > clip_box.x2) |
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((y > clip_box.y2) << 1) |
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((x < clip_box.x1) << 2) |
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((y < clip_box.y1) << 3);
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}
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//-------------------------------------------------------clip_liang_barsky
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template<class T>
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inline unsigned clip_liang_barsky(T x1, T y1, T x2, T y2,
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const rect_base<T>& clip_box,
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T* x, T* y)
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{
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const double nearzero = 1e-30;
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double deltax = x2 - x1;
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double deltay = y2 - y1;
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double xin;
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double xout;
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double yin;
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double yout;
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double tinx;
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double tiny;
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double toutx;
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double touty;
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double tin1;
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double tin2;
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double tout1;
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unsigned np = 0;
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if(deltax == 0.0)
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{
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// bump off of the vertical
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deltax = (x1 > clip_box.x1) ? -nearzero : nearzero;
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}
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if(deltay == 0.0)
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{
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// bump off of the horizontal
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deltay = (y1 > clip_box.y1) ? -nearzero : nearzero;
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}
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if(deltax > 0.0)
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{
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// points to right
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xin = clip_box.x1;
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xout = clip_box.x2;
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}
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else
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{
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xin = clip_box.x2;
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xout = clip_box.x1;
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}
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if(deltay > 0.0)
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{
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// points up
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yin = clip_box.y1;
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yout = clip_box.y2;
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}
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else
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{
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yin = clip_box.y2;
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yout = clip_box.y1;
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}
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tinx = (xin - x1) / deltax;
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tiny = (yin - y1) / deltay;
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if (tinx < tiny)
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{
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// hits x first
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tin1 = tinx;
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tin2 = tiny;
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}
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else
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{
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// hits y first
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tin1 = tiny;
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tin2 = tinx;
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}
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if(tin1 <= 1.0)
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{
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if(0.0 < tin1)
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{
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*x++ = (T)xin;
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*y++ = (T)yin;
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++np;
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}
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if(tin2 <= 1.0)
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{
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toutx = (xout - x1) / deltax;
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touty = (yout - y1) / deltay;
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tout1 = (toutx < touty) ? toutx : touty;
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if(tin2 > 0.0 || tout1 > 0.0)
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{
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if(tin2 <= tout1)
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{
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if(tin2 > 0.0)
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{
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if(tinx > tiny)
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{
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*x++ = (T)xin;
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*y++ = (T)(y1 + tinx * deltay);
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}
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else
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{
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*x++ = (T)(x1 + tiny * deltax);
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*y++ = (T)yin;
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}
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++np;
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}
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if(tout1 < 1.0)
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{
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if(toutx < touty)
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{
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*x++ = (T)xout;
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*y++ = (T)(y1 + toutx * deltay);
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}
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else
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{
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*x++ = (T)(x1 + touty * deltax);
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*y++ = (T)yout;
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}
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}
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else
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{
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*x++ = x2;
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*y++ = y2;
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}
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++np;
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}
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else
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{
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if(tinx > tiny)
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{
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*x++ = (T)xin;
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*y++ = (T)yout;
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}
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else
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{
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*x++ = (T)xout;
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*y++ = (T)yin;
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}
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++np;
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}
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}
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}
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}
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return np;
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}
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}
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#endif
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