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 WindowsFormsApplication6
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            Bitmap image = new Bitmap("C:\\Documents and Settings\\Beheerder\\Bureaublad\\PNG.png");
            pictureBox1.Image = image;

            BitmapData data = image.LockBits(new Rectangle(0, 0, image.Width, image.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
            unsafe
            {
                byte* ptr = (byte*)(data.Scan0);
                for (int i = 0; i < data.Height; i++)
                {
                    for (int j = 0; j < data.Width; j++)
                    {
                        // write the logic implementation here
                        ptr += 3;
                    }
                    ptr += data.Stride - data.Width * 3;
                }
            }
        }
    }
}

using System;
using System.Drawing;
using System.Drawing.Imaging;

namespace ConsoleApplication1 {
    class Program {
        static void Main(string[] args) {
            Bitmap srcBmp = new Bitmap("logo.gif");
            Bitmap dstBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
            for (int y = 0; y < srcBmp.Height; y++) {
                for (int x = 0; x < srcBmp.Width; x++) {
                    Color pix = srcBmp.GetPixel(x, y);
                    double greyLevel = pix.R*0.299 + pix.G*0.587 + pix.B*0.144;
                    if (greyLevel > 255) { greyLevel = 255; }
                    int g = (int)(greyLevel);
                    dstBmp.SetPixel(x, y, Color.FromArgb(0,g,0));
                }
            }
            dstBmp.Save("logo.png", ImageFormat.Png);
        }
    }
}