/// <summary> /// 使用byte[]数据,生成256色灰度 BMP 位图 /// </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); //将该位图存入内存中 MemoryStream curImageStream = new MemoryStream(); resultBitmap.Save(curImageStream, System.Drawing.Imaging.ImageFormat.Bmp); curImageStream.Flush(); //由于位图数据须要DWORD对齐(4byte倍数),计算须要补位的个数 int curPadNum = ((originalWidth * 8 + 31) / 32 * 4) - originalWidth; //终于生成的位图数据大小 int bitmapDataSize = ((originalWidth * 8 + 31) / 32 * 4) * originalHeight; //数据部分相对文件開始偏移。详细能够參考位图文件格式 int dataOffset = ReadData(curImageStream, 10, 4); //改变调色板,由于默认的调色板是32位彩色的,须要改动为256色的调色板 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); } //终于生成的位图数据。以及大小,高度没有变,宽度须要调整 byte[] destImageData = new byte[bitmapDataSize]; int destWidth = originalWidth + curPadNum; //生成终于的位图数据,注意的是。位图数据 从左到右,从下到上。所以须要颠倒 for (int originalRowIndex = originalHeight - 1; originalRowIndex >= 0; originalRowIndex--) { int destRowIndex = originalHeight - originalRowIndex - 1; for (int dataIndex = 0; dataIndex < originalWidth; dataIndex++) { //同一时候还要注意,新的位图数据的宽度已经变化destWidth,否则会产生错位 destImageData[destRowIndex * destWidth + dataIndex] = originalImageData[originalRowIndex * originalWidth + dataIndex]; } } //将流的Position移到数据段 curImageStream.Position = dataOffset; //将新位图数据写入内存中 curImageStream.Write(destImageData, 0, bitmapDataSize); curImageStream.Flush(); //将内存中的位图写入Bitmap对象 resultBitmap = new Bitmap(curImageStream); return resultBitmap; } /// <summary> /// 从内存流中指定位置,读取数据 /// </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> /// 向内存流中指定位置,写入数据 /// </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); }
转自:http://tech.sina.com.cn/s/2008-06-24/1206706116.shtml
时间: 2024-10-09 03:07:14