Transform VS Image Library icons for themes

Program.cs

using System;
using System.Xml.Linq;
using System.Linq;
using System.Collections.Generic;
using System.IO;
using SkiaSharp;

namespace VSIMageLib
{
    class Program
    {
        private static readonly XNamespace x = "http://schemas.microsoft.com/winfx/2006/xaml";

        static void Main(string[] args)
        {

            string inputFile = args[0];
            var backgroundColor = SKColor.Parse(args[1]); //ThemeBackgroundColor
            var outputFile =  args.Length == 3 ? args[2] : Path.Combine(Path.GetDirectoryName(inputFile), Path.GetFileNameWithoutExtension(inputFile) + ".Dark.xaml");

            var doc = XDocument.Load(inputFile);
            var currentBrushes = from element in doc.Descendants()
                                 where element.Attribute(x+"Key")?.Value?.StartsWith("VSImageLib", StringComparison.OrdinalIgnoreCase) == true
                                 from descendent in element.Descendants()
                                 let brush = descendent.Attribute("Brush")
                                 where brush is object
                                 select brush;

            backgroundColor.ToHsl(out var _, out var _, out var backgroundLuminosity);

            foreach (var brush in currentBrushes)
            {
                var color = SKColor.Parse(brush.Value);
                color.ToHsl(out var h, out var s, out var l);

                l = (float)SKTransformLuminosity(h,s,l,backgroundLuminosity);

                brush.Value = SKColor.FromHsl(h, s, l, color.Alpha).ToString();
            }

            doc.Save(outputFile);
        }

        private static double SKTransformLuminosity(double hue, double saturation, double luminosity, double backgroundLuminosity)
            => TransformLuminosity(hue, saturation / 100.0, luminosity / 100.0, backgroundLuminosity / 100.0) * 100.0;

        private static double TransformLuminosity(double hue, double saturation, double luminosity, double backgroundLuminosity)
        {
            if (backgroundLuminosity < 0.5)
            {
                if (luminosity >= 82.0 / 85.0)
                    return backgroundLuminosity * (luminosity - 1.0) / (-3.0 / 85.0);
                double val2 = saturation >= 0.2 ? (saturation <= 0.3 ? 1.0 - (saturation - 0.2) / (1.0 / 10.0) : 0.0) : 1.0;
                double num1 = Math.Max(Math.Min(1.0, Math.Abs(hue - 37.0) / 20.0), val2);
                double num2 = ((backgroundLuminosity - 1.0) * 0.66 / (82.0 / 85.0) + 1.0) * num1 + 0.66 * (1.0 - num1);
                if (luminosity < 0.66)
                    return (num2 - 1.0) / 0.66 * luminosity + 1.0;
                return (num2 - backgroundLuminosity) / (-259.0 / 850.0) * (luminosity - 82.0 / 85.0) + backgroundLuminosity;
            }
            if (luminosity < 82.0 / 85.0)
                return luminosity * backgroundLuminosity / (82.0 / 85.0);
            return (1.0 - backgroundLuminosity) * (luminosity - 1.0) / (3.0 / 85.0) + 1.0;
        }
    }
}