/// <summary>
/// 使用byte[]數據，生成256色灰度　BMP 位圖
/// </summary>
/// <param name="originalImageData"></param>
/// <param name="originalWidth"></param>
/// <param name="originalHeight"></param>
/// <returns></returns>
        public static Bitmap CreateBitmap(byte[] originalImageData, 
 
int originalWidth, int originalHeight)
{
//指定8位格式。即256色
            Bitmap resultBitmap = new Bitmap(originalWidth, originalHeight, System.Drawing.Imaging.PixelFormat.Format8bppIndexed);
//將該位圖存入內存中
            MemoryStream curImageStream = new MemoryStream();
resultBitmap.Save(curImageStream, System.Drawing.Imaging.ImageFormat.Bmp);
curImageStream.Flush();
 
//由於位圖數據須要DWORD對齊（4byte倍數），計算須要補位的個數
            int curPadNum = ((originalWidth * 8 + 31) / 32 * 4) - originalWidth;
//終於生成的位圖數據大小
            int bitmapDataSize = ((originalWidth * 8 + 31) / 32 * 4) * originalHeight;
//數據部分相對文件開始偏移。詳細能夠參考位圖文件格式
            int dataOffset = ReadData(curImageStream, 10, 4);
 
//改變調色板，由於默認的調色板是32位彩色的，須要改動為256色的調色板
            int paletteStart = 54;
int paletteEnd = dataOffset;
int color = 0;
for (int i = paletteStart; i < paletteEnd; i += 4)
{
byte[] tempColor = new byte[4];
tempColor[0] = (byte)color;
tempColor[1] = (byte)color;
tempColor[2] = (byte)color;
tempColor[3] = (byte)0;
color++;
curImageStream.Position = i;
curImageStream.Write(tempColor, 0, 4);
}
//終於生成的位圖數據。以及大小，高度沒有變，寬度須要調整
            byte[] destImageData = new byte[bitmapDataSize];
int destWidth = originalWidth + curPadNum;
//生成終於的位圖數據，註意的是。位圖數據 從左到右，從下到上。所以須要顛倒
            for (int originalRowIndex = originalHeight - 1; originalRowIndex >= 0; originalRowIndex--)
{
int destRowIndex = originalHeight - originalRowIndex - 1;
for (int dataIndex = 0; dataIndex < originalWidth; dataIndex++)
{
//同一時候還要註意，新的位圖數據的寬度已經變化destWidth，否則會產生錯位
                    destImageData[destRowIndex * destWidth + dataIndex] = originalImageData[originalRowIndex * originalWidth + dataIndex];
}
}
//將流的Position移到數據段   
            curImageStream.Position = dataOffset;
//將新位圖數據寫入內存中
            curImageStream.Write(destImageData, 0, bitmapDataSize);
curImageStream.Flush();
//將內存中的位圖寫入Bitmap對象
            resultBitmap = new Bitmap(curImageStream);
return resultBitmap;
}
/// <summary>
/// 從內存流中指定位置，讀取數據
/// </summary>
/// <param name="curStream"></param>
/// <param name="startPosition"></param>
/// <param name="length"></param>
/// <returns></returns>
        public static int ReadData(MemoryStream curStream, int startPosition, int length)
{
int result = -1;
byte[] tempData = new byte[length];
curStream.Position = startPosition;
curStream.Read(tempData, 0, length);
result = BitConverter.ToInt32(tempData, 0);
return result;
}
/// <summary>
/// 向內存流中指定位置，寫入數據
/// </summary>
/// <param name="curStream"></param>
/// <param name="startPosition"></param>
/// <param name="length"></param>
/// <param name="value"></param>
        public static void WriteData(MemoryStream curStream, int startPosition, int length, int value)
{
curStream.Position = startPosition;
curStream.Write(BitConverter.GetBytes(value), 0, length);
}

轉自：http://tech.sina.com.cn/s/2008-06-24/1206706116.shtml

C#中使用byte[]數據，生成Bitmap