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Diffstat (limited to 'agg/source/agg_bezier_arc.cpp')
| -rwxr-xr-x | agg/source/agg_bezier_arc.cpp | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/agg/source/agg_bezier_arc.cpp b/agg/source/agg_bezier_arc.cpp new file mode 100755 index 000000000000..6b47fff76fc8 --- /dev/null +++ b/agg/source/agg_bezier_arc.cpp @@ -0,0 +1,237 @@ +//---------------------------------------------------------------------------- +// Anti-Grain Geometry - Version 2.3 +// 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 +//---------------------------------------------------------------------------- +// +// Arc generator. Produces at most 4 consecutive cubic bezier curves, i.e., +// 4, 7, 10, or 13 vertices. +// +//---------------------------------------------------------------------------- + + +#include <math.h> +#include "agg_bezier_arc.h" + + +namespace agg +{ + + //------------------------------------------------------------arc_to_bezier + void arc_to_bezier(double cx, double cy, double rx, double ry, + double start_angle, double sweep_angle, + double* curve) + { + double x0 = cos(sweep_angle / 2.0); + double y0 = sin(sweep_angle / 2.0); + double tx = (1.0 - x0) * 4.0 / 3.0; + double ty = y0 - tx * x0 / y0; + double px[4]; + double py[4]; + px[0] = x0; + py[0] = -y0; + px[1] = x0 + tx; + py[1] = -ty; + px[2] = x0 + tx; + py[2] = ty; + px[3] = x0; + py[3] = y0; + + double sn = sin(start_angle + sweep_angle / 2.0); + double cs = cos(start_angle + sweep_angle / 2.0); + + unsigned i; + for(i = 0; i < 4; i++) + { + curve[i * 2] = cx + rx * (px[i] * cs - py[i] * sn); + curve[i * 2 + 1] = cy + ry * (px[i] * sn + py[i] * cs); + } + } + + + + //------------------------------------------------------------------------ + void bezier_arc::init(double x, double y, + double rx, double ry, + double start_angle, + double sweep_angle) + { + start_angle = fmod(start_angle, 2.0 * pi); + if(sweep_angle >= 2.0 * pi) sweep_angle = 2.0 * pi; + if(sweep_angle <= -2.0 * pi) sweep_angle = -2.0 * pi; + + double total_sweep = 0.0; + double local_sweep = 0.0; + m_num_vertices = 2; + bool done = false; + do + { + if(sweep_angle < 0.0) + { + local_sweep = -pi * 0.5; + total_sweep -= pi * 0.5; + if(total_sweep <= sweep_angle) + { + local_sweep = sweep_angle - (total_sweep + pi * 0.5); + done = true; + } + } + else + { + local_sweep = pi * 0.5; + total_sweep += pi * 0.5; + if(total_sweep >= sweep_angle) + { + local_sweep = sweep_angle - (total_sweep - pi * 0.5); + done = true; + } + } + + arc_to_bezier(x, y, rx, ry, + start_angle, + local_sweep, + m_vertices + m_num_vertices - 2); + + m_num_vertices += 6; + start_angle += local_sweep; + } + while(!done && m_num_vertices < 26); + } + + + + + //-------------------------------------------------------------------- + void bezier_arc_svg::init(double x0, double y0, + double rx, double ry, + double angle, + bool large_arc_flag, + bool sweep_flag, + double x2, double y2) + { + m_radii_ok = true; + + if(rx < 0.0) rx = -rx; + if(ry < 0.0) ry = -rx; + + // Calculate the middle point between + // the current and the final points + //------------------------ + double dx2 = (x0 - x2) / 2.0; + double dy2 = (y0 - y2) / 2.0; + + // Convert angle from degrees to radians + //------------------------ + double cos_a = cos(angle); + double sin_a = sin(angle); + + // Calculate (x1, y1) + //------------------------ + double x1 = cos_a * dx2 + sin_a * dy2; + double y1 = -sin_a * dx2 + cos_a * dy2; + + // Ensure radii are large enough + //------------------------ + double prx = rx * rx; + double pry = ry * ry; + double px1 = x1 * x1; + double py1 = y1 * y1; + + // Check that radii are large enough + //------------------------ + double radii_check = px1/prx + py1/pry; + if(radii_check > 1.0) + { + rx = sqrt(radii_check) * rx; + ry = sqrt(radii_check) * ry; + prx = rx * rx; + pry = ry * ry; + if(radii_check > 10.0) m_radii_ok = false; + } + + // Calculate (cx1, cy1) + //------------------------ + double sign = (large_arc_flag == sweep_flag) ? -1.0 : 1.0; + double sq = (prx*pry - prx*py1 - pry*px1) / (prx*py1 + pry*px1); + double coef = sign * sqrt((sq < 0) ? 0 : sq); + double cx1 = coef * ((rx * y1) / ry); + double cy1 = coef * -((ry * x1) / rx); + + // + // Calculate (cx, cy) from (cx1, cy1) + //------------------------ + double sx2 = (x0 + x2) / 2.0; + double sy2 = (y0 + y2) / 2.0; + double cx = sx2 + (cos_a * cx1 - sin_a * cy1); + double cy = sy2 + (sin_a * cx1 + cos_a * cy1); + + // Calculate the start_angle (angle1) and the sweep_angle (dangle) + //------------------------ + double ux = (x1 - cx1) / rx; + double uy = (y1 - cy1) / ry; + double vx = (-x1 - cx1) / rx; + double vy = (-y1 - cy1) / ry; + double p, n; + + // Calculate the angle start + //------------------------ + n = sqrt(ux*ux + uy*uy); + p = ux; // (1 * ux) + (0 * uy) + sign = (uy < 0) ? -1.0 : 1.0; + double v = p / n; + if(v < -1.0) v = -1.0; + if(v > 1.0) v = 1.0; + double start_angle = sign * acos(v); + + // Calculate the sweep angle + //------------------------ + n = sqrt((ux*ux + uy*uy) * (vx*vx + vy*vy)); + p = ux * vx + uy * vy; + sign = (ux * vy - uy * vx < 0) ? -1.0 : 1.0; + v = p / n; + if(v < -1.0) v = -1.0; + if(v > 1.0) v = 1.0; + double sweep_angle = sign * acos(v); + if(!sweep_flag && sweep_angle > 0) + { + sweep_angle -= pi * 2.0; + } + else + if (sweep_flag && sweep_angle < 0) + { + sweep_angle += pi * 2.0; + } + + // We can now build and transform the resulting arc + //------------------------ + m_arc.init(0.0, 0.0, rx, ry, start_angle, sweep_angle); + trans_affine mtx = trans_affine_rotation(angle); + mtx *= trans_affine_translation(cx, cy); + + for(unsigned i = 2; i < m_arc.num_vertices()-2; i += 2) + { + mtx.transform(m_arc.vertices() + i, m_arc.vertices() + i + 1); + } + + // We must make sure that the starting and ending points + // exactly coincide with the initial (x0,y0) and (x2,y2) + m_arc.vertices()[0] = x0; + m_arc.vertices()[1] = y0; + if(m_arc.num_vertices() > 2) + { + m_arc.vertices()[m_arc.num_vertices() - 2] = x2; + m_arc.vertices()[m_arc.num_vertices() - 1] = y2; + } + } + + +} |