Ptr VS Marshal
===
###### tags: `C# Image`
參考資料
http://yy-programer.blogspot.com/2012/08/c.html


using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;


namespace ImageArray
{
    class Program
    {
        public static byte[] RGB2ArrayMarshal(Bitmap srcBitmap)
        {
            int width = srcBitmap.Width;
            int height = srcBitmap.Height;
            int len​​gth = height * 3 * width;
            byte[] RGB = new byte[length];
            BitmapData data = srcBitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
            System.Runtime.InteropServices.Marshal.Copy(data.Scan0, RGB, 0, RGB.Length);
            srcBitmap.UnlockBits(data);
            return RGB;
        }

        public static byte[] RGB2ArrayPtr(Bitmap srcBitmap)
        {
            BitmapData sourceData = srcBitmap.LockBits(new Rectangle(0, 0, srcBitmap.Width, srcBitmap.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
            IntPtr source_scan = sourceData.Scan0;
            int length = srcBitmap.Width * srcBitmap.Height;
            byte[] RGB = new byte[length];
            unsafe
            {
                byte* source_p = (byte*)source_scan.ToPointer();
                for (int i = 0; i < length; i++)
                {
                    RGB[i] = (byte)source_p[0];
                }
                /*
                byte* source_p = (byte*)source_scan.ToPointer();
                for (int h = 0; h < srcBitmap.Height; h++)
                {
                    for (int w = 0; w < sourceData.Width; w++)
                    {
                        source_p[0] = 255;  //A
                        source_p++;
                        source_p[0] = 255;  //R
                        source_p++;
                        source_p[0] = 155;  //G
                        source_p++;
                        source_p[0] = 55;   //B
                        source_p++;
                    }
                }
                */
            }
            srcBitmap.UnlockBits(sourceData);
            return RGB;
        }


        static void Main(string[] args)
        {
            string path = @"C:\Users\Lee\Desktop\FHDImage.bmp";
            Bitmap bmp = new Bitmap(path);

            byte[] array;
            Stopwatch stopwatch = new Stopwatch();
            stopwatch.Start();
            for (int i = 0; i < 100; i++)
            {
                array = RGB2ArrayMarshal(bmp);
            }
            stopwatch.Stop();
            Console.WriteLine(string.Format("Marshal x 100 = {0}", stopwatch.ElapsedMilliseconds.ToString()));

            stopwatch.Reset();
            stopwatch.Start();
            byte[] array2;
            for (int i = 0; i<100; i++)
            {
                array2 = RGB2ArrayPtr(bmp);
            }
            stopwatch.Stop();
            Console.WriteLine(string.Format("Ptr x 100 = {0}", stopwatch.ElapsedMilliseconds.ToString()));
            Console.Read();
        }
    }
}