/// <summary>Prepare for decompressing frames</summary>
/// <remarks>
/// This method has to be called before GetBitmap and ExportBitmap.
/// Release ressources with GetFrameClose.
/// </remarks>
public void GetFrameOpen()
{
GetStreamInfo(StreamPointer);
//Open frames
Avi.BITMAPINFOHEADER bih = new Avi.BITMAPINFOHEADER();
bih.biBitCount = CountBitsPerPixel;
bih.biClrImportant = 0;
bih.biClrUsed = 0;
bih.biCompression = 0;
bih.biPlanes = 1;
bih.biSize = Marshal.SizeOf(bih);
bih.biXPelsPerMeter = 0;
bih.biYPelsPerMeter = 0;
// Corrections by M. Covington:
// If these are pre-set, interlaced video is not handled correctly.
// Better to give zeroes and let Windows fill them in.
bih.biHeight = 0; // was (Int32)streamInfo.rcFrame.bottom;
bih.biWidth = 0; // was (Int32)streamInfo.rcFrame.right;
// Corrections by M. Covington:
// Validate the bit count, because some AVI files give a bit count
// that is not one of the allowed values in a BitmapInfoHeader.
// Here 0 means for Windows to figure it out from other information.
if (bih.biBitCount > 24)
{
bih.biBitCount = 32;
}
else if (bih.biBitCount > 16)
{
bih.biBitCount = 24;
}
else if (bih.biBitCount > 8)
{
bih.biBitCount = 16;
}
else if (bih.biBitCount > 4)
{
bih.biBitCount = 8;
}
else if (bih.biBitCount > 0)
{
bih.biBitCount = 4;
}
getFrameObject = Avi.AVIStreamGetFrameOpen(StreamPointer, ref bih);
if (getFrameObject == 0)
{
throw new Exception("Exception in VideoStreamGetFrameOpen!");
}
}
/// <summary>Apply a format to a new stream</summary>
/// <param name="aviStream">The IAVISTREAM</param>
/// <remarks>
/// The format must be set before the first frame can be written,
/// and it cannot be changed later.
/// </remarks>
private void SetFormat(IntPtr aviStream)
{
Avi.BITMAPINFOHEADER bi = new Avi.BITMAPINFOHEADER();
bi.biSize = Marshal.SizeOf(bi);
bi.biWidth = Width;
bi.biHeight = Height;
bi.biPlanes = 1;
bi.biBitCount = CountBitsPerPixel;
bi.biSizeImage = FrameSize;
int result = Avi.AVIStreamSetFormat(aviStream, 0, ref bi, bi.biSize);
if (result != 0)
{
throw new Exception("Error in VideoStreamSetFormat: " + result);
}
}
/// <summary>Initialize a VideoStream for an existing stream</summary>
/// <param name="aviFile">The file that contains the stream</param>
/// <param name="aviStream">An IAVISTREAM from [aviFile]</param>
public VideoStream(int aviFile, IntPtr aviStream)
{
this.aviFile = aviFile;
this.aviStream = aviStream;
Avi.BITMAPINFOHEADER bih = new Avi.BITMAPINFOHEADER();
int size = Marshal.SizeOf(bih);
Avi.AVIStreamReadFormat(aviStream, 0, ref bih, ref size);
Avi.AVISTREAMINFO streamInfo = GetStreamInfo(aviStream);
FrameRate = (float)streamInfo.dwRate / (float)streamInfo.dwScale;
Width = (int)streamInfo.rcFrame.right;
Height = (int)streamInfo.rcFrame.bottom;
FrameSize = bih.biSizeImage;
CountBitsPerPixel = bih.biBitCount;
FirstFrame = Avi.AVIStreamStart(aviStream.ToInt32());
CountFrames = Avi.AVIStreamLength(aviStream.ToInt32());
}
/// <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);
}
