Shawn Weisfeld [MVP]

Image Processing v2

I was tearing into v1.5 of Microsoft Robotics Studio (http://www.microsoft.com/robotics) and came across a novel way to process the pixels in an image. In previous posts I was using unmanaged C# code and pointers to move around the image. This worked well but is hard to manage. They take the approach of just dumping the entire image to a byte[], pure genius, now why did I not think of that. I will be rebuilding my library to utilize this technique but I thought this was so cool that I just had to share it!

/// <summary>
/// Coverts a bitmap to a byte[] then prints out the contents to a file
/// </summary>
public void PrintImage()
{
    string file = "image.bmp";
    Bitmap bitmap = Bitmap.FromFile(file) as Bitmap;
    byte[] frame = ConvertBitmap(bitmap);
    int height = bitmap.Height;
    int width = bitmap.Width;

    using (StreamWriter sWriter = new StreamWriter(file + ".txt"))
    {
        int offset;

        //header
        sWriter.WriteLine(string.Format("({0}, {1}) {2},{3},{4}", "COL", "ROW", "RED", "GREEN", "BLUE"));

        //loop over rows
        for (int y = 0; y < height; y++)
        {
            offset = y * width * 3;

            //loop ober columns
            for (int x = 0; x < width; x++, offset += 3)
            {
                int r, g, b;

                b = frame[offset];
                g = frame[offset + 1];
                r = frame[offset + 2];

                //pixel information
                sWriter.WriteLine(string.Format("({0}, {1}) {2},{3},{4}", x, y, r, g, b));
            }
        }
    }
}

/// <summary>
/// Convert a bitmap to a byte array
/// </summary>
/// <param name="bitmap">image to convert</param>
/// <returns>image as bytes</returns>
private byte[] ConvertBitmap(Bitmap bitmap)
{
    //Code excerpted from Microsoft Robotics Studio v1.5
    BitmapData raw = null;  //used to get attributes of the image
    byte[] rawImage = null; //the image as a byte[]

    try
    {
        //Freeze the image in memory
        raw = bitmap.LockBits(
            new Rectangle(0, 0, (int)bitmap.Width, (int)bitmap.Height),
            ImageLockMode.ReadOnly,
            PixelFormat.Format24bppRgb
        );

        int size = raw.Height * raw.Stride;
        rawImage = new byte[size];

        //Copy the image into the byte[]
        System.Runtime.InteropServices.Marshal.Copy(raw.Scan0, rawImage, 0, size);
    }
    finally
    {
        if (raw != null)
        {
            //Unfreeze the memory for the image
            bitmap.UnlockBits(raw);
        }
    }
    return rawImage;
}