CSharpImageLibrary.DDS.DDSGeneral.BuildMipMaps C# (CSharp) Method

        internal static int BuildMipMaps(List<MipMap> MipMaps)
        {
            if (MipMaps?.Count == 0)
                return 0;

            MipMap currentMip = MipMaps[0];

            // KFreon: Check if mips required
            int estimatedMips = DDSGeneral.EstimateNumMipMaps(currentMip.Width, currentMip.Height);
            if (MipMaps.Count > 1)
                return estimatedMips;

            // KFreon: Half dimensions until one == 1.
            MipMap[] newmips = new MipMap[estimatedMips];

            var baseBMP = UsefulThings.WPF.Images.CreateWriteableBitmap(currentMip.Pixels, currentMip.Width, currentMip.Height);
            baseBMP.Freeze();

            Action<int> action = new Action<int>(item =>
            {
                int index = item;
                MipMap newmip;
                var scale = 1d / (2 << (index - 1));  // Shifting is 2^index - Math.Pow seems extraordinarly slow.
                newmip = ImageEngine.Resize(baseBMP, scale, scale, currentMip.Width, currentMip.Height);
                newmips[index - 1] = newmip;
            });

            // Start at 1 to skip top mip
            if (ImageEngine.EnableThreading)
                Parallel.For(1, estimatedMips + 1, new ParallelOptions { MaxDegreeOfParallelism = ImageEngine.NumThreads }, action);
            else
                for (int item = 1; item < estimatedMips + 1; item++)
                    action(item);

            MipMaps.AddRange(newmips);
            return estimatedMips;
        }