Alpha.cs

using System.Threading.Tasks;
using SkiaSharp;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Graphs.Functions.Colors
{
    public class Alpha : FunctionTwoScalarVariables
    {
        public Alpha(ScriptNode Color, ScriptNode Alpha, int Start, int Length, Expression Expression)
            : base(Color, Alpha, Start, Length, Expression)
        {
        }
 
        public override string[] DefaultArgumentNames => new string[] { "Color", "Alpha" };
 
        public override string FunctionName => nameof(Alpha);
 
        public override bool UpgradeScalarsToSameSet => false;
 
        public override IElement EvaluateScalar(IElement Argument1, IElement Argument2, Variables Variables)
        {
            return this.Evaluate(Argument1.AssociatedObjectValue, Argument2.AssociatedObjectValue);
        }
 
        public override Task<IElement> EvaluateScalarAsync(IElement Argument1, IElement Argument2, Variables Variables)
        {
            return Task.FromResult<IElement>(this.Evaluate(Argument1.AssociatedObjectValue, Argument2.AssociatedObjectValue));
        }
 
        private IElement Evaluate(object Argument1, object Argument2)
        { 
            SKColor Color = Graph.ToColor(Argument1);
            double Alpha = Expression.ToDouble(Argument2);
            byte A;
 
            if (Alpha < 0)
                A = 0;
            else if (Alpha > 255)
                A = 255;
            else
                A = (byte)(Alpha + 0.5);
 
            return new ObjectValue(new SKColor(Color.Red, Color.Green, Color.Blue, A));
        }
 
        public override IElement EvaluateScalar(string Argument1, string Argument2, Variables Variables)
        {
            return this.Evaluate(Argument1, Argument2);
        }
    }
}