QuickLook/QuickLook.Plugin/QuickLook.Plugin.HtmlViewer/UrlHelper.cs

using System.IO;
using System.Text;

namespace QuickLook.Plugin.HtmlViewer
{
    internal static class UrlHelper
    {
        internal static string FilePathToFileUrl(string filePath)
        {
            var uri = new StringBuilder();
            foreach (var v in filePath)
                if (v >= 'a' && v <= 'z' || v >= 'A' && v <= 'Z' || v >= '0' && v <= '9' ||
                    v == '+' || v == '/' || v == ':' || v == '.' || v == '-' || v == '_' || v == '~' ||
                    v > '\xFF')
                    uri.Append(v);
                else if (v == Path.DirectorySeparatorChar || v == Path.AltDirectorySeparatorChar)
                    uri.Append('/');
                else
                    uri.Append($"%{(int) v:X2}");
            if (uri.Length >= 2 && uri[0] == '/' && uri[1] == '/') // UNC path
                uri.Insert(0, "file:");
            else
                uri.Insert(0, "file:///");
            return uri.ToString();
        }
    }
}