Overlay RSI

using System;
using cAlgo.API;
using cAlgo.API.Internals;
using cAlgo.API.Indicators;
using cAlgo.Indicators;

namespace cAlgo
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
    public class OverlayRSI : Indicator
    {
        [Parameter(DefaultValue = "Close")]
        public DataSeries Source { get; set; }

        [Parameter(DefaultValue = 14, MinValue = 1)]
        public int Period { get; set; }

        [Parameter(DefaultValue = 50, MinValue = 0, MaxValue =100)]
        public int BackgroundOpacity { get; set; }

        [Parameter(DefaultValue = 30, MinValue = 0, MaxValue =100, Step = 1, Group ="Levels")]
        public double UpperLevel { get; set; }
        [Parameter(DefaultValue = "dimgray", Group = "Levels")]
        public string UpperColor { get; set; }

        [Parameter(DefaultValue = 70, MinValue = 0, MaxValue =100, Step = 1, Group = "Levels")]
        public double LowerLevel { get; set; }
        [Parameter(DefaultValue = "dimgray", MinValue = 0, MaxValue = 100, Step = 1, Group = "Levels")]
        public string LowerColor { get; set; }

        [Output("RSI")]
        public IndicatorDataSeries Result { get; set; }

        private RelativeStrengthIndex _rsi;
        private ChartHorizontalLine _upperLine;
        private ChartHorizontalLine _lowerLine;
        private ChartRectangle _backRect;
        private double _convert(double val) { return val * (_upperLine.Y - _lowerLine.Y) / 100 + _lowerLine.Y; }

        protected override void Initialize()
        {
            _rsi = Indicators.RelativeStrengthIndex(Source, Period);
            var color = Chart.ColorSettings.ForegroundColor;
            _upperLine = Chart.DrawHorizontalLine("upper_line", (Chart.TopY-Chart.BottomY)*0.9+Chart.BottomY, color, 1, LineStyle.Dots);
            _lowerLine = Chart.DrawHorizontalLine("lower_line", (Chart.TopY - Chart.BottomY) * 0.1 + Chart.BottomY, color, 1, LineStyle.Dots);
            _backRect = Chart.DrawRectangle("back_rect", Bars.OpenTimes[0], _upperLine.Y, Time+TimeSpan.FromDays(360) , _lowerLine.Y, Color.FromArgb(BackgroundOpacity, color));
            _backRect.IsFilled = true;
            var upperLevel = Chart.DrawHorizontalLine("upper_leves", _convert(UpperLevel), Color.FromName(UpperColor), 1, LineStyle.DotsVeryRare);
            var lowerLevel = Chart.DrawHorizontalLine("lower_leves", _convert(LowerLevel), Color.FromName(LowerColor), 1, LineStyle.DotsVeryRare);
            _upperLine.IsInteractive = _lowerLine.IsInteractive = true;

            Chart.ObjectUpdated += args => {
                var name = args.ChartObject.Name;
                if (name == _upperLine.Name || name == _lowerLine.Name) {
                    _backRect.Y1 = _upperLine.Y;
                    _backRect.Y2 = _lowerLine.Y;
                    upperLevel.Y = _convert(UpperLevel);
                    lowerLevel.Y = _convert(LowerLevel);
                    for (int i = 0; i < Bars.Count; i++) Calculate(i);
                }
            };

        }

        public override void Calculate(int index)
        {
            Result[index] = _convert(_rsi.Result[index]);
        }
    }
}