WPF C#

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="BitmapProgramming" Height="300" Width="300">
  

//File:Window.xaml.cs
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
namespace BitmapProgramming
{
    public partial class ModifyPixels : System.Windows.Window
    {
        public ModifyPixels()
        {
            InitializeComponent();
            BitmapImage originalBmp = new BitmapImage();
            originalBmp.BeginInit();
            originalBmp.UriSource = new Uri("http://www.your host.com/a.jpeg");
            originalBmp.DownloadCompleted += delegate{
                BitmapSource prgbaSource = new FormatConvertedBitmap(originalBmp,PixelFormats.Pbgra32, null, 0);
                WriteableBitmap bmp = new WriteableBitmap(prgbaSource);
                int w = 20;
                int h = 30;
                int[] pixelData = new int[w * h];
                int widthInBytes = 4 * w;
                bmp.CopyPixels(pixelData, widthInBytes, 0);
                for (int i = 0; i < pixelData.Length; ++i)
                {
                    pixelData[i] ^= 0x00112233;
                }
                bmp.WritePixels(new Int32Rect(0, 0, w, h),pixelData, widthInBytes, 0);
                imageElement.Source = bmp;
            };
            originalBmp.EndInit();
        }
    }
}