Bitmap和byte[]的相互转换

        /// <summary>
        /// 将Bitmap转换为字节数组
        /// </summary>
        /// <param name="width">图像宽度</param>
        /// <param name="height">图像长度</param>
        /// <param name="channel">图像通道</param>
        /// <param name="img">原图像</param>
        /// <returns></returns>
        public static byte[] getByteStreamFromBitmap(int width, int height, int channel, Bitmap img)
        {
            byte[] bytes = new byte[width * height * channel];
            BitmapData im = img.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, img.PixelFormat);
            int stride = im.Stride;
            int offset = stride - width * channel;
            int length = stride * height;
            byte[] temp = new byte[stride * height];
            Marshal.Copy(im.Scan0, temp, 0, temp.Length);
            img.UnlockBits(im);
            int posreal = 0;
            int posscan = 0;
            for (int c = 0; c < height; c++)
            {
                for (int d = 0; d < width * channel; d++)
                {
                    bytes[posreal++] = temp[posscan++];
                }
                posscan += offset;
            }
            return bytes;
        }

        /// <summary>
        /// 将一个字节数组转换为8bit灰度位图
        /// </summary>
        /// <param name="rawValues">显示字节数组</param>
        /// <param name="width">图像宽度</param>
        /// <param name="height">图像高度</param>
        /// <returns>位图</returns>
        public static Bitmap ToGrayBitmap(byte[] rawValues, int width, int height)
        {
            //申请目标位图的变量，并将其内存区域锁定
            Bitmap bmp = new Bitmap(width, height, PixelFormat.Format8bppIndexed);
            BitmapData bmpData = bmp.LockBits(new Rectangle(0, 0, width, height),
            ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed);

            //获取图像参数
            int stride = bmpData.Stride;  // 扫描线的宽度
            int offset = stride - width;  // 显示宽度与扫描线宽度的间隙
            IntPtr iptr = bmpData.Scan0;  // 获取bmpData的内存起始位置
            int scanBytes = stride * height;// 用stride宽度，表示这是内存区域的大小  

            //下面把原始的显示大小字节数组转换为内存中实际存放的字节数组
            int posScan = 0, posReal = 0;// 分别设置两个位置指针，指向源数组和目标数组
            byte[] pixelValues = new byte[scanBytes];  //为目标数组分配内存  

            for (int x = 0; x < height; x++)
            {
                //下面的循环节是模拟行扫描
                for (int y = 0; y < width; y++)
                {
                    pixelValues[posScan++] = rawValues[posReal++];
                }
                posScan += offset;  //行扫描结束，要将目标位置指针移过那段“间隙”
            }

            //用Marshal的Copy方法，将刚才得到的内存字节数组复制到BitmapData中
            System.Runtime.InteropServices.Marshal.Copy(pixelValues, 0, iptr, scanBytes);
            bmp.UnlockBits(bmpData);  // 解锁内存区域  

            //下面的代码是为了修改生成位图的索引表，从伪彩修改为灰度
            ColorPalette tempPalette;
            using (Bitmap tempBmp = new Bitmap(1, 1, PixelFormat.Format8bppIndexed))
            {
                tempPalette = tempBmp.Palette;
            }
            for (int i = 0; i < 256; i++)
            {
                tempPalette.Entries[i] = Color.FromArgb(i, i, i);
            }

            bmp.Palette = tempPalette;

            //算法到此结束，返回结果
            return bmp;
        }