using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace JYControl
{
	/// <summary>
	/// Manager for color
	/// </summary>
	public class LBColorManager : Object
	{
		public static double BlendColour(double fg, double bg, double alpha)
		{
			double result = bg + (alpha * (fg - bg));
			if (result < 0.0)
				result = 0.0;
			if (result > 255)
				result = 255;
			return result;
		}

		public static Color StepColor(Color clr, int alpha)
		{
			if (alpha == 100)
				return clr;

			byte a = clr.A;
			byte r = clr.R;
			byte g = clr.G;
			byte b = clr.B;
			float bg = 0;

			int _alpha = Math.Min(alpha, 200);
			_alpha = Math.Max(alpha, 0);
			double ialpha = ((double)(_alpha - 100.0)) / 100.0;

			if (ialpha > 100)
			{
				// blend with white
				bg = 255.0F;
				ialpha = 1.0F - ialpha;  // 0 = transparent fg; 1 = opaque fg
			}
			else
			{
				// blend with black
				bg = 0.0F;
				ialpha = 1.0F + ialpha;  // 0 = transparent fg; 1 = opaque fg
			}

			r = (byte)(LBColorManager.BlendColour(r, bg, ialpha));
			g = (byte)(LBColorManager.BlendColour(g, bg, ialpha));
			b = (byte)(LBColorManager.BlendColour(b, bg, ialpha));

			return Color.FromArgb(a, r, g, b);
		}
	};
}