MS CE C# 获取dgn文件缩略图

Question

老师我想获取dgn文件的缩略图代码如下： 
 
 但是FromStream()去一直抛异常说参数无效，请问一下获取到的这个byte[]难道没有有效的图像格式？ 
 或者还有其他办法获取缩略图吗？

郑 岗 · Answer

public class DgnThumbnail
 {
 [DllImport("GdiPlus.dll", CharSet = CharSet.Unicode)]
 private static extern int GdipCreateBitmapFromGdiDib(IntPtr pBIH, IntPtr pPix, out IntPtr pBitmap);
 public static Bitmap CreateThumbnail(DgnFile df)
 {
 byte[] thumbnail = df.Thumbnail;
 Bitmap image = null;
 if (thumbnail != null)
 {
 IntPtr num = Marshal.AllocHGlobal(thumbnail.Length - 4);
 Marshal.Copy(thumbnail, 4, num, thumbnail.Length - 4);

 try
 {
 IntPtr pPix = new IntPtr(num.ToInt64() + (long)Marshal.SizeOf(typeof(Structs.BITMAPINFOHEADER)) + 1024L);
 MethodInfo method = typeof(Bitmap).GetMethod("FromGDIplus", BindingFlags.Static | BindingFlags.NonPublic);
 if (method != (MethodInfo)null)
 {
 IntPtr pBitmap = IntPtr.Zero;
 if (GdipCreateBitmapFromGdiDib(num, pPix, out pBitmap) == 0)
 {
 if (pBitmap != IntPtr.Zero)
 image= (Bitmap)method.Invoke((object)null, new object[1]
 {(object) pBitmap
 });
 }
 }
 
 }
 catch (Exception ex)
 {

 }
 finally {
 Marshal.FreeHGlobal(num);
 }
 
 }
 return image;
 }
 } 
 我简单写了一个类，具体代码自己研究 
 例子示意图：