private IEnumerable <Poly> BackgroundPolys()
{
var fullCirlce = (float)Math.PI * 2f;
var fullRadius0 = 0f;
var fullRadius1 = _worldDimensions.HsvColorPickerHueSaturationCircleRadius;
var fullRadiusRange = fullRadius1 - fullRadius0;
const int cirRes = 36;
const int radRes = 20;
var alphaDelta = fullCirlce / cirRes;
var radiusDelta = fullRadiusRange / radRes;
var ci = new CircularIterator(cirRes, true);
while (ci.Next() && ci.Alpha1Ratio <= 1.00000001f)
{
var rad0 = fullRadius0;
for (int rIx = 1; rIx <= radRes; ++rIx)
{
var rad1 = fullRadius0 + rIx * radiusDelta;
var p0 = new SKPoint(ci.Cos0 * rad0, ci.Sin0 * rad0) + _worldDimensions.Center;
var p1 = new SKPoint(ci.Cos1 * rad0, ci.Sin1 * rad0) + _worldDimensions.Center;
var p2 = new SKPoint(ci.Cos1 * rad1, ci.Sin1 * rad1) + _worldDimensions.Center;
var p3 = new SKPoint(ci.Cos0 * rad1, ci.Sin0 * rad1) + _worldDimensions.Center;
_hsvRgb.Hsv2Rgb(ci.Alpha0 / fullCirlce, (rad0 - fullRadius0) / fullRadiusRange, 1f, out SKColor c0);
_hsvRgb.Hsv2Rgb(ci.Alpha1 / fullCirlce, (rad0 - fullRadius0) / fullRadiusRange, 1f, out SKColor c1);
_hsvRgb.Hsv2Rgb(ci.Alpha1 / fullCirlce, (rad1 - fullRadius0) / fullRadiusRange, 1f, out SKColor c2);
_hsvRgb.Hsv2Rgb(ci.Alpha0 / fullCirlce, (rad1 - fullRadius0) / fullRadiusRange, 1f, out SKColor c3);
var poly = new Poly();
poly.Points.Add(p0);
poly.Points.Add(p1);
poly.Points.Add(p2);
poly.Points.Add(p3);
poly.Colors.Add(c0);
poly.Colors.Add(c1);
poly.Colors.Add(c2);
poly.Colors.Add(c3);
yield return(poly);
rad0 = rad1;
}
}
}
public void Draw(SKCanvas canvas, float scale)
{
var vs = Vertices().Select(v => new SKPoint(v.X * scale, v.Y * scale));
var cpl = new ColorPositionLine(_colorPositions.AsArray());
var ci = new CircularIterator(_circularResolution, false);
var cs = new List <SKColor>();
while (ci.Next())
{
var c0 = cpl.ColorAt(ci.Alpha0Ratio);
cs.Add(c0);
cs.Add(c0);
}
canvas.DrawVertices(SKVertexMode.TriangleStrip, vs.ToArray(), cs.ToArray(), new SKPaint());
}
private SKPoint[] Vertices()
{
if (_vertices == null)
{
var ci = new CircularIterator(_circularResolution, true);
var vs = new List <SKPoint>();
var r0 = _radius - _thickness / 2f;
var r1 = _radius + _thickness / 2f;
while (ci.Next())
{
var v0 = _center + new SKPoint(ci.Cos0 * r0, ci.Sin0 * r0);
var v1 = _center + new SKPoint(ci.Cos0 * r1, ci.Sin0 * r1);
vs.Add(v0);
vs.Add(v1);
}
_vertices = vs.ToArray();
}
return(_vertices);
}
