Pinta.ImageManipulation.ColorBgra.BlendColorsWAIP C# (CSharp) Method

        public static ColorBgra BlendColorsWAIP(ColorBgra[] c, uint[] w)
        {
            if (c.Length != w.Length)
            {
                throw new ArgumentException("c.Length != w.Length");
            }

            if (c.Length == 0)
            {
                return ColorBgra.FromUInt32(0);
            }

            long wsum = 0;
            long asum = 0;

            for (int i = 0; i < w.Length; ++i)
            {
                wsum += w[i];
                asum += c[i].A * w[i];
            }

            uint a = (uint)((asum + (wsum >> 1)) / wsum);

            long b;
            long g;
            long r;

            if (a == 0)
            {
                b = 0;
                g = 0;
                r = 0;
            }
            else
            {
                b = 0;
                g = 0;
                r = 0;

                for (int i = 0; i < c.Length; ++i)
                {
                    b += (long)c[i].A * c[i].B * w[i];
                    g += (long)c[i].A * c[i].G * w[i];
                    r += (long)c[i].A * c[i].R * w[i];
                }

                b /= asum;
                g /= asum;
                r /= asum;
            }

            return ColorBgra.FromUInt32((uint)b + ((uint)g << 8) + ((uint)r << 16) + ((uint)a << 24));
        }