RGBLuminanceSource.monotouch.cs

using System.Drawing;
using System;
using MonoTouch.UIKit;
using MonoTouch.CoreGraphics;
using System.Runtime.InteropServices;


namespace ZXing
{
   public partial class RGBLuminanceSource
   {
      /// <summary>
      /// Only for compatibility to older version
      /// should be replace by BitmapLuminanceSource and the faster grayscale algorithm
      /// </summary>
      /// <param name="d"></param>
      /// <param name="W"></param>
      /// <param name="H"></param>
    	public RGBLuminanceSource(UIImage d) : base(d.CGImage.Width, d.CGImage.Height)
		{
			CalculateLuminance (d);
		}

		private void CalculateLuminance(UIImage d)
		{
			var imageRef = d.CGImage;
			var width = imageRef.Width;
			var height = imageRef.Height;
			var colorSpace = CGColorSpace.CreateDeviceRGB();

			var rawData = Marshal.AllocHGlobal(height * width * 4);

			try
         	{
				var context = new CGBitmapContext(rawData, width, height, 8, 4 * width, 
				                                  colorSpace, CGImageAlphaInfo.PremultipliedLast);

				context.DrawImage(new RectangleF(0.0f, 0.0f, (float)width, (float)height), imageRef);
					
				var pixelData = new byte[height * width * 4];
				Marshal.Copy(rawData, pixelData, 0, pixelData.Length);

				CalculateLuminance(pixelData, BitmapFormat.RGB32);
			}
			finally
			{
				Marshal.FreeHGlobal(rawData);
			}
		
		}
	}
}