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//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software
// is granted provided this copyright notice appears in all copies.
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
// mcseemagg@yahoo.com
// http://www.antigrain.com
//----------------------------------------------------------------------------
//
// Liang-Barsky clipping
//
//----------------------------------------------------------------------------
#ifndef AGG_CLIP_LIANG_BARSKY_INCLUDED
#define AGG_CLIP_LIANG_BARSKY_INCLUDED
#include "agg_basics.h"
namespace agg
{
//------------------------------------------------------------------------
enum clipping_flags_e
{
clipping_flags_x1_clipped = 4,
clipping_flags_x2_clipped = 1,
clipping_flags_y1_clipped = 8,
clipping_flags_y2_clipped = 2,
clipping_flags_x_clipped = clipping_flags_x1_clipped | clipping_flags_x2_clipped,
clipping_flags_y_clipped = clipping_flags_y1_clipped | clipping_flags_y2_clipped
};
//----------------------------------------------------------clipping_flags
// Determine the clipping code of the vertex according to the
// Cyrus-Beck line clipping algorithm
//
// | |
// 0110 | 0010 | 0011
// | |
// -------+--------+-------- clip_box.y2
// | |
// 0100 | 0000 | 0001
// | |
// -------+--------+-------- clip_box.y1
// | |
// 1100 | 1000 | 1001
// | |
// clip_box.x1 clip_box.x2
//
//
template<class T>
inline unsigned clipping_flags(T x, T y, const rect_base<T>& clip_box)
{
return (x > clip_box.x2) |
((y > clip_box.y2) << 1) |
((x < clip_box.x1) << 2) |
((y < clip_box.y1) << 3);
}
//--------------------------------------------------------clipping_flags_x
template<class T>
inline unsigned clipping_flags_x(T x, const rect_base<T>& clip_box)
{
return (x > clip_box.x2) | ((x < clip_box.x1) << 2);
}
//--------------------------------------------------------clipping_flags_y
template<class T>
inline unsigned clipping_flags_y(T y, const rect_base<T>& clip_box)
{
return ((y > clip_box.y2) << 1) | ((y < clip_box.y1) << 3);
}
//-------------------------------------------------------clip_liang_barsky
template<class T>
inline unsigned clip_liang_barsky(T x1, T y1, T x2, T y2,
const rect_base<T>& clip_box,
T* x, T* y)
{
const double nearzero = 1e-30;
double deltax = x2 - x1;
double deltay = y2 - y1;
double xin;
double xout;
double yin;
double yout;
double tinx;
double tiny;
double toutx;
double touty;
double tin1;
double tin2;
double tout1;
unsigned np = 0;
if(deltax == 0.0)
{
// bump off of the vertical
deltax = (x1 > clip_box.x1) ? -nearzero : nearzero;
}
if(deltay == 0.0)
{
// bump off of the horizontal
deltay = (y1 > clip_box.y1) ? -nearzero : nearzero;
}
if(deltax > 0.0)
{
// points to right
xin = clip_box.x1;
xout = clip_box.x2;
}
else
{
xin = clip_box.x2;
xout = clip_box.x1;
}
if(deltay > 0.0)
{
// points up
yin = clip_box.y1;
yout = clip_box.y2;
}
else
{
yin = clip_box.y2;
yout = clip_box.y1;
}
tinx = (xin - x1) / deltax;
tiny = (yin - y1) / deltay;
if (tinx < tiny)
{
// hits x first
tin1 = tinx;
tin2 = tiny;
}
else
{
// hits y first
tin1 = tiny;
tin2 = tinx;
}
if(tin1 <= 1.0)
{
if(0.0 < tin1)
{
*x++ = (T)xin;
*y++ = (T)yin;
++np;
}
if(tin2 <= 1.0)
{
toutx = (xout - x1) / deltax;
touty = (yout - y1) / deltay;
tout1 = (toutx < touty) ? toutx : touty;
if(tin2 > 0.0 || tout1 > 0.0)
{
if(tin2 <= tout1)
{
if(tin2 > 0.0)
{
if(tinx > tiny)
{
*x++ = (T)xin;
*y++ = (T)(y1 + tinx * deltay);
}
else
{
*x++ = (T)(x1 + tiny * deltax);
*y++ = (T)yin;
}
++np;
}
if(tout1 < 1.0)
{
if(toutx < touty)
{
*x++ = (T)xout;
*y++ = (T)(y1 + toutx * deltay);
}
else
{
*x++ = (T)(x1 + touty * deltax);
*y++ = (T)yout;
}
}
else
{
*x++ = x2;
*y++ = y2;
}
++np;
}
else
{
if(tinx > tiny)
{
*x++ = (T)xin;
*y++ = (T)yout;
}
else
{
*x++ = (T)xout;
*y++ = (T)yin;
}
++np;
}
}
}
}
return np;
}
//----------------------------------------------------------------------------
template<class T>
bool clip_move_point(T x1, T y1, T x2, T y2,
const rect_base<T>& clip_box,
T* x, T* y, unsigned flags)
{
T bound;
if(flags & clipping_flags_x_clipped)
{
if(x1 == x2)
{
return false;
}
bound = (flags & clipping_flags_x1_clipped) ? clip_box.x1 : clip_box.x2;
*y = (T)(double(bound - x1) * (y2 - y1) / (x2 - x1) + y1);
*x = bound;
}
flags = clipping_flags_y(*y, clip_box);
if(flags & clipping_flags_y_clipped)
{
if(y1 == y2)
{
return false;
}
bound = (flags & clipping_flags_y1_clipped) ? clip_box.y1 : clip_box.y2;
*x = (T)(double(bound - y1) * (x2 - x1) / (y2 - y1) + x1);
*y = bound;
}
return true;
}
//-------------------------------------------------------clip_line_segment
// Returns: ret >= 4 - Fully clipped
// (ret & 1) != 0 - First point has been moved
// (ret & 2) != 0 - Second point has been moved
//
template<class T>
unsigned clip_line_segment(T* x1, T* y1, T* x2, T* y2,
const rect_base<T>& clip_box)
{
unsigned f1 = clipping_flags(*x1, *y1, clip_box);
unsigned f2 = clipping_flags(*x2, *y2, clip_box);
unsigned ret = 0;
if((f2 | f1) == 0)
{
// Fully visible
return 0;
}
if((f1 & clipping_flags_x_clipped) != 0 &&
(f1 & clipping_flags_x_clipped) == (f2 & clipping_flags_x_clipped))
{
// Fully clipped
return 4;
}
if((f1 & clipping_flags_y_clipped) != 0 &&
(f1 & clipping_flags_y_clipped) == (f2 & clipping_flags_y_clipped))
{
// Fully clipped
return 4;
}
T tx1 = *x1;
T ty1 = *y1;
T tx2 = *x2;
T ty2 = *y2;
if(f1)
{
if(!clip_move_point(tx1, ty1, tx2, ty2, clip_box, x1, y1, f1))
{
return 4;
}
if(*x1 == *x2 && *y1 == *y2)
{
return 4;
}
ret |= 1;
}
if(f2)
{
if(!clip_move_point(tx1, ty1, tx2, ty2, clip_box, x2, y2, f2))
{
return 4;
}
if(*x1 == *x2 && *y1 == *y2)
{
return 4;
}
ret |= 2;
}
return ret;
}
}
#endif
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