using System;
using System.Diagnostics;

internal unsafe class Program
{
    private const int COUNT = 500;
    private const int WIDTH = 1920;
    private const int HEIGHT = 1080;

    private static void Main()
    {
        var image = new int[WIDTH * HEIGHT];

        for (int i = 0; i < 10; i++)
        {
            var time = TestOriginal(image, WIDTH, HEIGHT);
            Console.WriteLine("original: " + time);

            var time2 = Test(image, WIDTH, HEIGHT);
            Console.WriteLine("optimized: " + time2);
        }

        Console.ReadLine();
    }

    private static long TestOriginal(int[] image, int width, int height)
    {
        var sw = Stopwatch.StartNew();
        var buf = (int[])image.Clone();
        for (int n = 0; n < COUNT; n++)
        {
            for (int y = 1; y < height - 1; y++)
            {
                var p = width * y;
                for (int x = 1; x < width - 1; x++)
                    if (image[p + x] != 0xffffff)
                        buf[p + x] = (image[p - width + x] + image[p + x - 1] + image[p - width + x - 1] + image[p - width + x + 1] + image[p + width + x - 1] + image[p + width + x] + image[p + x + 1] + image[p + width + x + 1]) >> 3;
            }
            for (int y = 1; y < height - 1; y++)
            {
                var p = width * y;
                for (int x = 1; x < width - 1; x++)
                    if (buf[p + x] != 0xffffff)
                        image[p + x] = (buf[p - width + x] + buf[p + x - 1] + buf[p - width + x - 1] + buf[p - width + x + 1] + buf[p + width + x - 1] + buf[p + width + x] + buf[p + x + 1] + buf[p + width + x + 1]) >> 3;
            }
        }
        sw.Stop();
        return sw.ElapsedMilliseconds;
    }

    private static long Test(int[] image, int width, int height)
    {
        var stopwatch = Stopwatch.StartNew();

        var buffer = new int[image.Length];
        for (int n = 0; n < COUNT; n++)
        {
            Blur(image, buffer, width, height);
            Blur(buffer, image, width, height);
        }

        stopwatch.Stop();
        return stopwatch.ElapsedMilliseconds;
    }

    private static void Blur(int[] input, int[] output, int width, int height)
    {
        fixed (int* inputPointer = input)
        {
            for (int y = 1; y < height - 1; y++)
            {
                int index = y * width;
                int* currentLine = inputPointer + index + 1;
                int* prevLine = currentLine - width;
                int* nextLine = currentLine + width;

                for (int x = 1; x < width - 1; x++)
                {
                    if (*currentLine != 0xffffff)
                    {
                        int sum = *(prevLine - 1) + *prevLine + *(++prevLine) +
                                  *(currentLine - 1) + *(++currentLine) +
                                  *(nextLine - 1) + *nextLine + *(++nextLine);
                        output[index + x] = sum >> 3;
                    }
                }
            }
        }
    }
}