是.net compact的bug还是方式不对？访问内存速度很慢。请高手进来探讨指点！

Question

程序的目的是把一段16bit的黑白bitmap对象按位转成一个byte[]，代码如下：
        private void PrintBitmap(ref Bitmap bmp, bool start, int start_sleep, bool stop, int stop_sleep)
        {
            int btsLenght=(104 + 104 / 2) * bmp.Width;
            if (PrintString)
                btsLenght *= 2;
            byte[] bts = new byte[btsLenght];
            int DataLenght = 0;
            byte[] OrBytes = new byte[8];
            for (int i = 7; i >= 0; i--)
            {
                OrBytes[i] = (byte)(1 << i);
            }
            int TempBufferLenght = PrintDataLength * 3 / 2;
            byte[] TempBuffer = new byte[TempBufferLenght];            int bmp_width = bmp.Width;
            int bmp_height = bmp.Height;            Rectangle rect = new Rectangle(0, 0, bmp_width, bmp_height);            //下面用非托管代码，指针操作
            unsafe
            {
                System.Drawing.Imaging.BitmapData bmpData = bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format16bppRgb555);
                short* ptr_begin = (short*)bmpData.Scan0;
                short* ptr = ptr_begin;                Stopwatch wc = new Stopwatch();
                wc.Start();//开始测试执行时间
                for (int x_value = 0; x_value < bmp_width; x_value++)
                {
                    int i = 0;
                    int j = 0;
                    Array.Clear(TempBuffer, 0, TempBufferLenght);
                    TempBuffer[j] = 0xfe;//头
                    TempBuffer[j + 1] = 0x01;//打印属性标志
                    j += 2;                    for (int y_value = 0; y_value < BitmapHeight; y_value++)
                    {
                        ptr = ptr_begin;
                        ptr += (y_value * bmp_width + x_value);//当前像素的地址
                        if (*ptr == 0)
                        {
                            TempBuffer[j] |= OrBytes[i];
                            if ((TempBuffer[j] == 0xfd) || (TempBuffer[j] == 0xfe) || (TempBuffer[j] == 0xff))
                            {
                                TempBuffer[j + 1] = (byte)(TempBuffer[j] ^ 0x20);
                                TempBuffer[j] = 0xfd;
                                j++;
                            }
                        }
                        i++;
                        if (i == 8)
                        {
                            j++;
                            i = 0;
                        }
                    }
                    TempBuffer[j] = 0xff;
                    byte[] DataBuffer = new byte[j + 1];
                    Buffer.BlockCopy(TempBuffer, 0, bts, DataLenght, j + 1);
                    if (PrintString)
                    {
                        DataLenght += (j + 1);
                        Buffer.BlockCopy(TempBuffer, 0, bts, DataLenght, j + 1);
                    }
                    DataLenght += (j + 1);
                }
                bmp.UnlockBits(bmpData);
                wc.Stop();//结束测试执行时间
                MessageBox.Show(wc.ElapsedMilliseconds.ToString());
                 PrintSerial.WritePort(bts, DataLenght);
            }
        }在2440平台上测试运行时间为：1700多ms  如果改成下面的代码，速度就提高到400多ms ，难道C#访问内存速度会如此之慢？真是难以理解。按说用指针直接访问内存不会有那么大的差别呀。（为了提速，指针访问方式是从short[]访问方式改过来的，托管方式一样慢）
        private void PrintBitmap(ref Bitmap bmp, bool start, int start_sleep, bool stop, int stop_sleep)
        {
            int btsLenght=(104 + 104 / 2) * bmp.Width;
            if (PrintString)
                btsLenght *= 2;
            byte[] bts = new byte[btsLenght];
            int DataLenght = 0;
            byte[] OrBytes = new byte[8];
            for (int i = 7; i >= 0; i--)
            {
                OrBytes[i] = (byte)(1 << i);
            }
            int TempBufferLenght = PrintDataLength * 3 / 2;
            byte[] TempBuffer = new byte[TempBufferLenght];            int bmp_width = bmp.Width;
            int bmp_height = bmp.Height;            Rectangle rect = new Rectangle(0, 0, bmp_width, bmp_height); 
            //下面用非托管代码，指针操作
            unsafe
            {
                System.Drawing.Imaging.BitmapData bmpData = bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format16bppRgb555);
                short* ptr_begin = (short*)bmpData.Scan0;
                short* ptr = ptr_begin;                Stopwatch wc = new Stopwatch();
                wc.Start();//开始测试执行时间
                for (int x_value = 0; x_value < bmp_width; x_value++)
                {
                    int i = 0;
                    int j = 0;
                    Array.Clear(TempBuffer, 0, TempBufferLenght);
                    TempBuffer[j] = 0xfe;//头
                    TempBuffer[j + 1] = 0x01;//打印属性标志
                    j += 2;                    for (int y_value = 0; y_value < BitmapHeight; y_value++)
                    {
                        ptr = ptr_begin;
                        ptr += (y_value * bmp_width + x_value);//当前像素的地址
                        int iii = 1000;// *ptr;//
                        if (iii == 0)
                        {
                            TempBuffer[j] |= OrBytes[i];
                            if ((TempBuffer[j] == 0xfd) || (TempBuffer[j] == 0xfe) || (TempBuffer[j] == 0xff))
                            {
                                TempBuffer[j + 1] = (byte)(TempBuffer[j] ^ 0x20);
                                TempBuffer[j] = 0xfd;
                                j++;
                            }
                        }
                        i++;
                        if (i == 8)
                        {
                            j++;
                            i = 0;
                        }
                    }
                    TempBuffer[j] = 0xff;
                    byte[] DataBuffer = new byte[j + 1];
                    Buffer.BlockCopy(TempBuffer, 0, bts, DataLenght, j + 1);
                    if (PrintString)
                    {
                        DataLenght += (j + 1);
                        Buffer.BlockCopy(TempBuffer, 0, bts, DataLenght, j + 1);
                    }
                    DataLenght += (j + 1);
                }
                bmp.UnlockBits(bmpData);
                wc.Stop();//结束测试执行时间
                PrintSerial.WritePort(bts, DataLenght);
            }
        }

Answer 1

应该不是Bug，应该是代码上的问题，~

Answer 2

if (*ptr == 0)和int iii = 1000;// *ptr;//
if (iii == 0)

Answer 3

good good study,day day up

Answer 4

怎么我测试的结果是相差很小呢？
是否if (*ptr == 0)这个条件实际成立了，而下面的是始终不成立的。

Answer 5

不是这样的 成立的很少。问题出在*ptr就很慢。有可能你不是跑ce程序的原因

Answer 6

你这个条件 不一样 不能作为这个结果的证据的 
和int iii = 1000;// ;//
if (iii == 0)
对于*ptr 你的像素有白色的 就会成立的另外图片 还有空白空间的
你可以使用*ptr
当然 需要真实的环境中去运行的，如果在模拟器中运行的话。ptr肯定慢点、。

Answer 7

不是在模拟器上运行的。*ptr慢体现出来是访问内存慢。