Make an image black and white in c#. For more information: http://eric.tumblr.com/post/71459461047/make-an-image-black-and-white-in-c

BlackAndWhite.cs

private static Bitmap BlackAndWhite(Bitmap image, Rectangle rectangle)
{
    Bitmap blackAndWhite = new System.Drawing.Bitmap(image.Width, image.Height);
 
    // make an exact copy of the bitmap provided
    using(Graphics graphics = System.Drawing.Graphics.FromImage(blackAndWhite))
        graphics.DrawImage(image, new System.Drawing.Rectangle(0, 0, image.Width, image.Height),
            new Rectangle(0, 0, image.Width, image.Height), GraphicsUnit.Pixel);
 
    // for every pixel in the rectangle region
    for (Int32 xx = rectangle.X; xx < rectangle.X + rectangle.Width && xx < image.Width; xx++)
    {
        for (Int32 yy = rectangle.Y; yy < rectangle.Y + rectangle.Height && yy < image.Height; yy++)
        {
            // average the red, green and blue of the pixel to get a gray value
            Color pixel = blackAndWhite.GetPixel(xx, yy);
            Int32 avg = (pixel.R + pixel.G + pixel.B) / 3;
 
            blackAndWhite.SetPixel(xx, yy, Color.FromArgb(0, avg, avg, avg));
        }
    }
 
    return blackAndWhite;
}

MakeGrayscale3.cs

// from http://www.switchonthecode.com/tutorials/csharp-tutorial-convert-a-color-image-to-grayscale

public static Bitmap MakeGrayscale3(Bitmap original)
{
   //create a blank bitmap the same size as original
   Bitmap newBitmap = new Bitmap(original.Width, original.Height);
 
   //get a graphics object from the new image
   Graphics g = Graphics.FromImage(newBitmap);
 
   //create the grayscale ColorMatrix
   ColorMatrix colorMatrix = new ColorMatrix(
      new float[][]
      {
         new float[] {.3f, .3f, .3f, 0, 0},
         new float[] {.59f, .59f, .59f, 0, 0},
         new float[] {.11f, .11f, .11f, 0, 0},
         new float[] {0, 0, 0, 1, 0},
         new float[] {0, 0, 0, 0, 1}
      });
 
   //create some image attributes
   ImageAttributes attributes = new ImageAttributes();
 
   //set the color matrix attribute
   attributes.SetColorMatrix(colorMatrix);
 
   //draw the original image on the new image
   //using the grayscale color matrix
   g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height),
      0, 0, original.Width, original.Height, GraphicsUnit.Pixel, attributes);
 
   //dispose the Graphics object
   g.Dispose();
   return newBitmap;
}

usage.cs

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