public static IEnumerable <Point> Enumerate(int radiusX, int radiusY, bool filled = false)
{
// preliminary check - zero point
if (radiusX == 0 || radiusY == 0)
{
return(Enumerable.Empty <Point>());
}
// preliminary check - horizontal line
if (radiusY == 1 || radiusY == -1)
{
return(LineRasterizer.EnumerateHorizontalLine(radiusX));
}
// preliminary check - vertical line
if (radiusX == 1 || radiusX == -1)
{
return(LineRasterizer.EnumerateVerticalLine(radiusY));
}
// potencial problem - negative radius X
if (radiusX < 0)
{
radiusX = -radiusX;
}
// potencial problem - negative radius Y
if (radiusY < 0)
{
radiusY = -radiusY;
}
// enumerates ellipse
return(EnumerateEllipse(radiusX, radiusY, filled));
}
/// <summary>
/// If you wonder why I didn't use some faster algorithm (bresenham, mid-point..) it's because it wouldn't match
/// the outline of drawn ellipse via Graphics.DrawEllipse. So the obstacle looks elsewhere then the drawn ellipse.
/// TODO revisit in a few years.
/// </summary>
private static IEnumerable <Point> EnumerateEllipse(int radiusX, int radiusY, bool filled = false)
{
double anomaly = HalfPi;
Point lastPoint = Point.Empty;
List <Point> result = new List <Point>
{
new Point(-radiusX, radiusY),
new Point(radiusX, radiusY)
};
if (filled)
{
result.Add(Point.Empty);
}
while (anomaly >= 0.0)
{
int shiftX = Convert.ToInt32(radiusX * Math.Cos(anomaly));
int shiftY = Convert.ToInt32(radiusY * Math.Sin(anomaly));
int x = radiusX + shiftX;
int y = radiusY + shiftY;
if (x != lastPoint.X || y != lastPoint.Y)
{
Point topLeft = new Point(radiusX - shiftX, radiusY - shiftY);
Point topRight = new Point(radiusX + shiftX, radiusY - shiftY);
Point bottomLeft = new Point(radiusX - shiftX, radiusY + shiftY);
Point bottomRight = new Point(radiusX + shiftX, radiusY + shiftY);
result.Add(topLeft);
if (filled)
{
result.AddRange(LineRasterizer.EnumerateHorizontalLine(radiusX - shiftX + 1, radiusX + shiftX - 1, radiusY - shiftY));
}
result.Add(topRight);
result.Add(bottomLeft);
if (filled)
{
result.AddRange(LineRasterizer.EnumerateHorizontalLine(radiusX - shiftX + 1, radiusX + shiftX - 1, radiusY + shiftY));
}
result.Add(bottomRight);
lastPoint = bottomRight;
}
anomaly -= Step;
}
return(result);
}
