public static void Arc(Cairo.Context context, PointF p, double r, double a1, double a2, bool clockwise, Color color, bool filled, double width = 1.0)
{
context.Save();
context.Translate(p.X, p.Y);
if (!filled)
{
context.LineWidth = width;
context.LineCap = Cairo.LineCap.Butt;
context.LineJoin = Cairo.LineJoin.Bevel;
}
var c = color.ToCairo();
context.SetSourceRGBA(c.R, c.G, c.B, c.A);
if (clockwise)
{
context.Arc(0, 0, r, a1, a2);
}
else
{
context.ArcNegative(0, 0, r, a1, a2);
}
if (filled)
{
context.Fill();
}
else
{
context.Stroke();
}
context.Restore();
}
private void DrawArcSegment(double xm1, double ym1, double xm2, double ym2, double xr, double yr, double alpha, bool isLargeArc, SweepDirection direction)
{
if (xr <= 0.000000001 || yr <= 0.000000001)
{
return;
}
var x1 = xm1 * Math.Cos(-alpha) - ym1 * Math.Sin(-alpha);
var y1 = xm1 * Math.Sin(-alpha) + ym1 * Math.Cos(-alpha);
var x2 = xm2 * Math.Cos(-alpha) - ym2 * Math.Sin(-alpha);
var y2 = xm2 * Math.Sin(-alpha) + ym2 * Math.Cos(-alpha);
var r = 0.0;
if (xr > yr)
{
y1 = y1 * xr / yr;
y2 = y2 * xr / yr;
r = xr;
}
else
{
x1 = x1 * yr / xr;
x2 = x2 * yr / xr;
r = yr;
}
if (4 * r * r < (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2))
{
return;
}
var xc1 = 0.0;
var xc2 = 0.0;
var yc1 = 0.0;
var yc2 = 0.0;
if (Math.Abs(y1 - y2) > 0.000000001)
{
var A = (x1 - x2) / (y2 - y1);
var B = (x2 * x2 - x1 * x1 + y2 * y2 - y1 * y1) / (2 * (y2 - y1));
var a = A * A + 1;
var b = -2 * x1 + 2 * A * B - 2 * A * y1;
var c = x1 * x1 + B * B - 2 * B * y1 + y1 * y1 - r * r;
xc1 = (-b + Math.Sqrt(b * b - 4 * a * c)) / (2 * a);
yc1 = A * xc1 + B;
xc2 = (-b - Math.Sqrt(b * b - 4 * a * c)) / (2 * a);
yc2 = A * xc2 + B;
}
else
{
xc1 = (x1 + x2) / 2;
yc1 = y1 + Math.Sqrt(r * r - (xc1 - x1) * (xc1 - x1));
xc2 = (x1 + x2) / 2;
yc2 = y1 - Math.Sqrt(r * r - (xc2 - x1) * (xc2 - x1));
}
var angle1 = Math.Abs(y1 - yc1) / r > 1 ? Math.PI / 2 : Math.Asin(Math.Abs(y1 - yc1) / r);
if ((x1 < xc1) && (y1 >= yc1))
{
angle1 = Math.PI - angle1;
}
if (y1 < yc1)
{
if (x1 < xc1)
{
angle1 = Math.PI + angle1;
}
else
{
angle1 = -angle1;
}
}
var angle2 = Math.Abs(y2 - yc1) / r > 1 ? Math.PI / 2 : Math.Asin(Math.Abs(y2 - yc1) / r);
if ((x2 < xc1) && (y2 >= yc1))
{
angle2 = Math.PI - angle2;
}
if (y2 < yc1)
{
if (x2 < xc1)
{
angle2 = Math.PI + angle2;
}
else
{
angle2 = -angle2;
}
}
var alfa1 = Math.Abs(y1 - yc2) / r > 1 ? Math.PI / 2 : Math.Asin(Math.Abs(y1 - yc2) / r);
if ((x1 < xc2) && (y1 >= yc2))
{
alfa1 = Math.PI - alfa1;
}
if (y1 < yc2)
{
if (x1 < xc2)
{
alfa1 = Math.PI + alfa1;
}
else
{
alfa1 = -alfa1;
}
}
var alfa2 = Math.Abs(y2 - yc2) / r > 1 ? Math.PI / 2 : Math.Asin(Math.Abs(y2 - yc2) / r);
if ((x2 < xc2) && (y2 >= yc2))
{
alfa2 = Math.PI - alfa2;
}
if (y2 < yc2)
{
if (x2 < xc2)
{
alfa2 = Math.PI + alfa2;
}
else
{
alfa2 = -alfa2;
}
}
cr.Save();
cr.Rotate(alpha);
if (xr > yr)
{
cr.Scale(1, yr / xr);
}
else
{
cr.Scale(xr / yr, 1);
}
if (direction == SweepDirection.Clockwise)
{
if (isLargeArc)
{
if ((y1 < y2) || ((Math.Abs(y1 - y2) < 0.00000001) && (x1 > x2)))
{
cr.Arc(xc1, yc1, r, angle1, angle2);
}
else
{
cr.Arc(xc2, yc2, r, alfa1, alfa2);
}
}
else
{
if ((y1 > y2) || ((Math.Abs(y1 - y2) < 0.00000001) && (x1 < x2)))
{
cr.Arc(xc1, yc1, r, angle1, angle2);
}
else
{
cr.Arc(xc2, yc2, r, alfa1, alfa2);
}
}
}
else
{
if (isLargeArc)
{
if ((y1 > y2) || ((Math.Abs(y1 - y2) < 0.00000001) && (x1 < x2)))
{
cr.ArcNegative(xc1, yc1, r, angle1, angle2);
}
else
{
cr.ArcNegative(xc2, yc2, r, alfa1, alfa2);
}
}
else
{
if ((y1 < y2) || ((Math.Abs(y1 - y2) < 0.00000001) && (x1 > x2)))
{
cr.ArcNegative(xc1, yc1, r, angle1, angle2);
}
else
{
cr.ArcNegative(xc2, yc2, r, alfa1, alfa2);
}
}
}
cr.Restore();
}
