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摸索了3天,终于成功实现了使用已知byte[]数据,生成Bitmap(256色灰度 BMP位图)。
/// <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(); //由于位图数据需要DWORD对齐(4byte倍数),计算需要补位的个数 int curPadNum = ((originalWidth * 8 + 31) / 32 * 4) - originalWidth; //最终生成的位图数据大小 int bitmapDataSize = ((originalWidth * 8 + 31) / 32 * 4) * originalHeight; //数据部分相对文件开始偏移,具体可以参考位图文件格式 int dataOffset = ReadData(curImageStream, 10, 4); //改变调色板,因为默认的调色板是32位彩色的,需要修改为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); } //最终生成的位图数据,以及大小,高度没有变,宽度需要调整 byte[] destImageData = new byte[bitmapDataSize]; int destWidth = originalWidth + curPadNum; //生成最终的位图数据,注意的是,位图数据 从左到右,从下到上,所以需要颠倒 for (int originalRowIndex = originalHeight - 1; originalRowIndex >= 0; originalRowIndex--) { int destRowIndex = originalHeight - originalRowIndex - 1; for (int dataIndex = 0; dataIndex < originalWidth; dataIndex++) { //同时还要注意,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); } |
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