/// <summary>Export a frame into a bitmap</summary>
/// <param name="position">Position of the frame</param>
public Bitmap GetBitmap(int position)
{
if (position > CountFrames)
{
throw new Exception("Invalid frame position: " + position);
}
GetStreamInfo(StreamPointer);
//Decompress the frame and return a pointer to the DIB
int dib = Avi.AVIStreamGetFrame(getFrameObject, FirstFrame + position);
//Copy the bitmap header into a managed struct
Avi.BITMAPINFOHEADER bih = new Avi.BITMAPINFOHEADER();
bih = (Avi.BITMAPINFOHEADER)Marshal.PtrToStructure(new IntPtr(dib), bih.GetType());
if (bih.biSizeImage < 1)
{
throw new Exception("Exception in VideoStreamGetFrame");
}
//copy the image
byte[] bitmapData;
int address = dib + Marshal.SizeOf(bih);
if (bih.biBitCount < 16)
{
//copy palette and pixels
bitmapData = new byte[bih.biSizeImage + Avi.PALETTE_SIZE];
}
else
{
//copy only pixels
bitmapData = new byte[bih.biSizeImage];
}
Marshal.Copy(new IntPtr(address), bitmapData, 0, bitmapData.Length);
//copy bitmap info
byte[] bitmapInfo = new byte[Marshal.SizeOf(bih)];
IntPtr ptr;
ptr = Marshal.AllocHGlobal(bitmapInfo.Length);
Marshal.StructureToPtr(bih, ptr, false);
address = ptr.ToInt32();
Marshal.Copy(new IntPtr(address), bitmapInfo, 0, bitmapInfo.Length);
Marshal.FreeHGlobal(ptr);
//create file header
Avi.BITMAPFILEHEADER bfh = new Avi.BITMAPFILEHEADER();
bfh.bfType = Avi.BMP_MAGIC_COOKIE;
bfh.bfSize = 55 + bih.biSizeImage; //size of file as written to disk
bfh.bfReserved1 = 0;
bfh.bfReserved2 = 0;
bfh.bfOffBits = Marshal.SizeOf(bih) + Marshal.SizeOf(bfh);
if (bih.biBitCount < 16)
{
//There is a palette between header and pixel data
bfh.bfOffBits += Avi.PALETTE_SIZE;
}
//write a bitmap stream
BinaryWriter bw = new BinaryWriter(new MemoryStream());
//write header
bw.Write(bfh.bfType);
bw.Write(bfh.bfSize);
bw.Write(bfh.bfReserved1);
bw.Write(bfh.bfReserved2);
bw.Write(bfh.bfOffBits);
//write bitmap info
bw.Write(bitmapInfo);
//write bitmap data
bw.Write(bitmapData);
Bitmap bmp = (Bitmap)Image.FromStream(bw.BaseStream);
Bitmap saveableBitmap = new Bitmap(bmp.Width, bmp.Height);
Graphics g = Graphics.FromImage(saveableBitmap);
g.DrawImage(bmp, 0, 0);
g.Dispose();
bmp.Dispose();
bw.Close();
return(saveableBitmap);
}
