Image Erosion for face detection in C#

I'm trying to implement face detection in C#. I currently have a black + white outline of a photo with a face within it (Here). However i'm now trying to remove the noise and then dilate the image in order to improve reliability when i implement the detection.

The method I have so far is here:

           using System;
using System.Collections.Generic
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Imaging;

namespace ImageErosion
{
    public partial class Form1 : Form
    {
        public int CompareEmptyColor { get; set; }

        public Form1()
        {
            InitializeComponent();
        }

        private void btErodeImage_Click(object sender, EventArgs e)
        {
            Image inputImage = pbInputImage.Image;

            Image result = Process(inputImage);

            pbInputImage.Image = result;
        }

        unsafe public Image Process(Image input)
        {
            Bitmap bmp = (Bitmap)input;
            Bitmap bmpSrc = (Bitmap)input;

            BitmapData bmData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height),
                                ImageLockMode.ReadWrite,
                                PixelFormat.Format1bppIndexed);

            int stride = bmData.Stride;
            int stride2 = bmData.Stride * 2;
            IntPtr Scan0 = bmData.Scan0;

            byte* p = (byte*)(void*)Scan0;

            int nOffset = stride - bmp.Width * 3;
            int nWidth = bmp.Width - 2;
            int nHeight = bmp.Height - 2;

            var w = bmp.Width;
            var h = bmp.Height;

            var rp = p;
            var empty = CompareEmptyColor;
            byte c, cm;
            int i = 0;

            // Erode every pixel
            for (int y = 0; y < h; y++)
            {
                for (int x = 0; x < w; x += 3, i++)
                {
                    // Middle pixel
                    cm = p[y * stride + x];
                    if (cm == empty) { continue; }

                    #region FirstRow
                    // Row 0
                    // Left pixel
                    if (x - 3 > 0 && y - 2 > 0)
                    {
                        c = p[(y - 2) * stride + (x - 3)];
                        if (c == empty) { continue; }
                    }
                    // Middle left pixel
                    if (x - 2 > 0 && y - 2 > 0)
                    {
                        c = p[(y - 2) * stride + (x - 2)];
                        if (c == empty) { continue; }
                    }
                    if (x - 1 > 0 && y - 2 > 0)
                    {
                        c = p[(y - 2) * stride + (x - 1)];
                        if (c == empty) { continue; }
                    }
                    if (y - 2 > 0)
                    {
                        c = p[(y - 2) * stride + x];
                        if (c == empty) { continue; }
                    }
                    if (x + 1 < w && y - 2 > 0)
                    {
                        c = p[(y - 2) * stride + (x + 1)];
                        if (c == empty) { continue; }
                    }
                    if (x + 2 < w && y - 2 > 0)
                    {
                        c = p[(y - 2) * stride + (x + 2)];
                        if (c == empty) { continue; }
                    }
                    if (x + 3 < w && y - 2 > 0)
                    {
                        c = p[(y - 2) * stride + (x + 3)];
                        if (c == empty) { continue; }
                    }
                    #endregion

                    #region SecondRow
                    // Row 1
                    // Left pixel 
                    if (x - 3 > 0 && y - 1 > 0)
                    {
                        c = p[(y - 1) * stride + (x - 3)];
                        if (c == empty) { continue; }
                    }
                    if (x - 2 > 0 && y - 1 > 0)
                    {
                        c = p[(y - 1) * stride + (x - 2)];
                        if (c == empty) { continue; }
                    }
                    if (x - 1 > 0 && y - 1 > 0)
                    {
                        c = p[(y - 1) * stride + (x - 1)];
                        if (c == empty) { continue; }
                    }
                    if (y - 1 > 0)
                    {
                        c = p[(y - 1) * stride + x];
                        if (c == empty) { continue; }
                    }
                    if (x + 1 < w && y - 1 > 0)
                    {
                        c = p[(y - 1) * stride + (x + 1)];
                        if (c == empty) { continue; }
                    }
                    if (x + 2 < w && y - 1 > 0)
                    {
                        c = p[(y - 1) * stride + (x + 2)];
                        if (c == empty) { continue; }
                    }
                    if (x + 3 < w && y - 1 > 0)
                    {
                        c = p[(y - 1) * stride + (x + 3)];
                        if (c == empty) { continue; }
                    }

                    #endregion

                    #region ThirdRow
                    // Row 2
                    if (x - 3 > 0)
                    {
                        c = p[y * stride + (x - 3)];
                        if (c == empty) { continue; }
                    }
                    if (x - 2 > 0)
                    {
                        c = p[y * stride + (x - 2)];
                        if (c == empty) { continue; }
                    }
                    if (x - 1 > 0)
                    {
                        c = p[y * stride + (x - 1)];
                        if (c == empty) { continue; }
                    }
                    if (x + 1 < w)
                    {
                        c = p[y * stride + (x + 1)];
                        if (c == empty) { continue; }
                    }
                    if (x + 2 < w)
                    {
                        c = p[y * stride + (x + 2)];
                        if (c == empty) { continue; }
                    }
                    if (x + 3 < w)
                    {
                        c = p[y * stride + (x + 3)];
                        if (c == empty) { continue; }
                    }
                    #endregion

                    #region FourthRow
                    // Row 3
                    if (x - 3 > 0 && y + 1 < h)
                    {
                        c = p[(y + 1) * stride + (x - 3)];
                        if (c == empty) { continue; }
                    }
                    if (x - 2 > 0 && y + 1 < h)
                    {
                        c = p[(y + 1) * stride + (x - 2)];
                        if (c == empty) { continue; }
                    }
                    if开发者_StackOverflow (x - 1 > 0 && y + 1 < h)
                    {
                        c = p[(y + 1) * stride + (x - 1)];
                        if (c == empty) { continue; }
                    }
                    if (y + 1 < h)
                    {
                        c = p[(y + 1) * stride + x];
                        if (c == empty) { continue; }
                    }
                    if (x + 1 < w && y + 1 < h)
                    {
                        c = p[(y + 1) * stride + (x + 1)];
                        if (c == empty) { continue; }
                    }
                    if (x + 2 < w && y + 1 < h)
                    {
                        c = p[(y + 1) * stride + (x + 2)];
                        if (c == empty) { continue; }
                    }
                    if (x + 3 < w && y + 1 < h)
                    {
                        c = p[(y + 1) * stride + (x + 3)];
                        if (c == empty) { continue; }
                    }
                    #endregion

                    #region FifthRow
                    // Row 4
                    if (x - 3 > 0 && y + 2 < h)
                    {
                        c = p[(y + 2) * stride + (x - 3)];
                        if (c == empty) { continue; }
                    }
                    if (x - 2 > 0 && y + 2 < h)
                    {
                        c = p[(y + 2) * stride + (x - 2)];
                        if (c == empty) { continue; }
                    }
                    if (x - 1 > 0 && y + 2 < h)
                    {
                        c = p[(y + 2) * stride + (x - 1)];
                        if (c == empty) { continue; }
                    }
                    if (y + 2 < h)
                    {
                        c = p[(y + 2) * stride + x];
                        if (c == empty) { continue; }
                    }
                    if (x + 1 < w && y + 2 < h)
                    {
                        c = p[(y + 2) * stride + (x + 1)];
                        if (c == empty) { continue; }
                    }
                    if (x + 2 < w && y + 2 < h)
                    {
                        c = p[(y + 2) * stride + (x + 2)];
                        if (c == empty) { continue; }
                    }
                    if (x + 3 < w && y + 2 < h)
                    {
                        c = p[(y + 2) * stride + (x + 3)];
                        if (c == empty) { continue; }
                    }
                    #endregion

                    // If all neighboring pixels are processed 
                    // it's clear that the current pixel is not a boundary pixel.
                    rp[i] = cm;
                }
            }

            bmpSrc.UnlockBits(bmData);
            return bmpSrc;
        }
    }
}

As I understand it, in order to erode the image (and remove the noise), we need to check each pixel to see if it's surrounding pixels are black, and if so, then it is a border pixel and we need not keep it, which i believe my code does, so it is beyond me why it doesn't work.

Any help or pointers would be greatly appreciated

Thanks, Chris

A couple of bugaboos that jump out. The image format is 24bpp but you are reading bytes. That could sorta work if it is a pure black+white image but the left pixel would be at x - 3. Indexing x by 3 would also be wise.

Indexing the row is wrong, you multiply by w, you should multiply by stride.

you should take a look at the AForge.net Library ( http://code.google.com/p/aforge/ ). There are many different filters available for images. There you can also find examples how you can modify images directly

Why dont you use openCV? Dilate is a direct function there and is generally more optimal for all images..