Pixelate an image with c#. More information: http://eric.tumblr.com/post/71459967718/pixelate-an-image-with-c

Pixelate.cs

private static Bitmap Pixelate(Bitmap image, Rectangle rectangle, Int32 pixelateSize)
{
    Bitmap pixelated = new System.Drawing.Bitmap(image.Width, image.Height);
 
    // make an exact copy of the bitmap provided
    using (Graphics graphics = System.Drawing.Graphics.FromImage(pixelated))
        graphics.DrawImage(image, new System.Drawing.Rectangle(0, 0, image.Width, image.Height),
            new Rectangle(0, 0, image.Width, image.Height), GraphicsUnit.Pixel);
 
    // look at every pixel in the rectangle while making sure we're within the image bounds
    for (Int32 xx = rectangle.X; xx < rectangle.X + rectangle.Width && xx < image.Width; xx += pixelateSize)
    {
        for (Int32 yy = rectangle.Y; yy < rectangle.Y + rectangle.Height && yy < image.Height; yy += pixelateSize)
        {
            Int32 offsetX = pixelateSize / 2;
            Int32 offsetY = pixelateSize / 2;
 
            // make sure that the offset is within the boundry of the image
            while (xx + offsetX >= image.Width) offsetX--;
            while (yy + offsetY >= image.Height) offsetY--;
 
            // get the pixel color in the center of the soon to be pixelated area
            Color pixel = pixelated.GetPixel(xx + offsetX, yy + offsetY);
 
            // for each pixel in the pixelate size, set it to the center color
            for (Int32 x = xx; x < xx + pixelateSize && x < image.Width; x++)
                for (Int32 y = yy; y < yy + pixelateSize && y < image.Height; y++)
                    pixelated.SetPixel(x, y, pixel);
        }
    }
 
    return pixelated;
}

PixelateOverloaded.cs

private static Bitmap Pixelate(Bitmap image, Int32 blurSize)
{
    return Pixelate(image, new Rectangle(0, 0, image.Width, image.Height), blurSize);
}