在AVI文件中隐藏信息

doriandeng

doriandeng

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2008-07-04 00:53 | 只看楼主 树型| 收藏| 小中大 1^#

在AVI文件中隐藏信息

Windows AVI 库是avifil32.dll中函数的集合. 使用之前先得用 AVIFileInit初始化. AVIFileOpen 打开文件, AVIFileGetStream 取得视频流. 这些函数申请的内存最后都必须释放. AVI文件可以包含四种不同类型的多个流,通常每种类型只有一个流,我们这里只关心视频流.

//Initialize the AVI library
[DllImport("avifil32.dll")]
public static extern void AVIFileInit();
//Open an AVI file
[DllImport("avifil32.dll", PreserveSig=true)]
public static extern int AVIFileOpen(
ref int ppfile,
String szFile,
int uMode,
int pclsidHandler);
//Get a stream from an open AVI file
[DllImport("avifil32.dll")]
public static extern int AVIFileGetStream(
int pfile,
out IntPtr ppavi,
int fccType,
int lParam);
//Release an open AVI stream
[DllImport("avifil32.dll")]
public static extern int AVIStreamRelease(IntPtr aviStream);
//Release an ope AVI file
[DllImport("avifil32.dll")]
public static extern int AVIFileRelease(int pfile);
//Close the AVI library
[DllImport("avifil32.dll")]
public static extern void AVIFileExit();
private int aviFile = 0;
private IntPtr aviStream;
public void Open(string fileName) {
AVIFileInit(); //Intitialize AVI library
//Open the file
int result = AVIFileOpen(
ref aviFile,
fileName,
OF_SHARE_DENY_WRITE, 0);
//Get the video stream
result = AVIFileGetStream(
aviFile,
out aviStream,
streamtypeVIDEO, 0);
}

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doriandeng

doriandeng

组别:管理员
性别:
积分:1783
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2008-07-04 00:53 | 只看楼主 树型| 收藏| 小中大 2^#

回复: 在AVI文件中隐藏信息

读帧之前,我们需要明了我们要读的东西: 第一个帧从哪里开始的?一共有多少帧?图像的高度宽度是多少?AVI库包含以下函数回答我们的上述问题

//Get the start position of a stream
[DllImport("avifil32.dll", PreserveSig=true)]
public static extern int AVIStreamStart(int pavi);
//Get the length of a stream in frames
[DllImport("avifil32.dll", PreserveSig=true)]
public static extern int AVIStreamLength(int pavi);
//Get header information about an open stream
[DllImport("avifil32.dll")]
public static extern int AVIStreamInfo(
int pAVIStream,
ref AVISTREAMINFO psi,
int lSize);

调用以上函数我们可以填充位图信息头BITMAPINFOHEADER 结构,然后我们用以下函数来提取帧

//Get a pointer to a GETFRAME object (returns 0 on error)
[DllImport("avifil32.dll")]
public static extern int AVIStreamGetFrameOpen(
IntPtr pAVIStream,
ref BITMAPINFOHEADER bih);
//Get a pointer to a packed DIB (returns 0 on error)
[DllImport("avifil32.dll")]
public static extern int AVIStreamGetFrame(
int pGetFrameObj,
int lPos);
//Release the GETFRAME object
[DllImport("avifil32.dll")]
public static extern int AVIStreamGetFrameClose(int pGetFrameObj);

准备工作就绪,现在解压帧

//get start position and count of frames
int firstFrame = AVIStreamStart(aviStream.ToInt32());
int countFrames = AVIStreamLength(aviStream.ToInt32());
//get header information
AVISTREAMINFO streamInfo = new AVISTREAMINFO();
result = AVIStreamInfo(aviStream.ToInt32(), ref streamInfo,
Marshal.SizeOf(streamInfo));
//construct the expected bitmap header
BITMAPINFOHEADER bih = new BITMAPINFOHEADER();
bih.biBitCount = 24;
bih.biCompression = 0; //BI_RGB;
bih.biHeight = (Int32)streamInfo.rcFrame.bottom;
bih.biWidth = (Int32)streamInfo.rcFrame.right;
bih.biPlanes = 1;
bih.biSize = (UInt32)Marshal.SizeOf(bih);
//prepare to decompress DIBs (device independend bitmaps)
int getFrameObject = AVIStreamGetFrameOpen(aviStream, ref bih);
//Export the frame at the specified position
public void ExportBitmap(int position, String dstFileName){
//Decompress the frame and return a pointer to the DIB
int pDib = Avi.AVIStreamGetFrame(getFrameObject, firstFrame + position);
//Copy the bitmap header into a managed struct
BITMAPINFOHEADER bih = new BITMAPINFOHEADER();
bih = (BITMAPINFOHEADER)Marshal.PtrToStructure(new IntPtr(pDib),
bih.GetType());
//Copy the image
byte[] bitmapData = new byte[bih.biSizeImage];
int address = pDib + Marshal.SizeOf(bih);
for(int offset=0; offset<bitmapData.Length; offset++){
bitmapData[offset] = Marshal.ReadByte(new IntPtr(address));
address++;
}
//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();
for(int offset=0; offset<bitmapInfo.Length; offset++){
bitmapInfo[offset] = Marshal.ReadByte(new IntPtr(address));
address++;
}

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doriandeng

doriandeng

组别:管理员
性别:
积分:1783
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2008-07-04 00:54 | 只看楼主 树型| 收藏| 小中大 3^#

回复: 在AVI文件中隐藏信息

然后保存为位图

//Create file header
Avi.BITMAPFILEHEADER bfh = new Avi.BITMAPFILEHEADER();
bfh.bfType = Avi.BMP_MAGIC_COOKIE;
//size of file as written to disk

bfh.bfSize = (Int32)(55 + bih.biSizeImage);
bfh.bfOffBits = Marshal.SizeOf(bih) + Marshal.SizeOf(bfh);
//Create or overwrite the destination file
FileStream fs = new FileStream(dstFileName, System.IO.FileMode.Create);
BinaryWriter bw = new BinaryWriter(fs);
//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);
bw.Close();
fs.Close();
} //end of ExportBitmap

应用程序会把解出来的位图当作普通位图来隐藏信息,如果载体文件是AVI文件,则提取第一帧到一个临时位图文件,放入一些信息,接下来是第二帧...最后一帧之后则关闭AVI文件,删除临时位图文件,接下来处理下一个载体文件.

应用程序块打开AVI 载体文件时, 它创建另一个AVI文件来保存新的位图,新的文件大小和帧频率都与原来的一样, 我们不能用 Open() 来创建,而使用AVIFileCreateStream, AVIStreamSetFormat and AVIStreamWrite:

//Create a new stream in an open AVI file
[DllImport("avifil32.dll")]
public static extern int AVIFileCreateStream(
int pfile,
out IntPtr ppavi,
ref AVISTREAMINFO ptr_streaminfo);
//Set the format for a new stream
[DllImport("avifil32.dll")]
public static extern int AVIStreamSetFormat(
IntPtr aviStream, Int32 lPos,
ref BITMAPINFOHEADER lpFormat, Int32 cbFormat);
//Write a sample to a stream
[DllImport("avifil32.dll")]
public static extern int AVIStreamWrite(
IntPtr aviStream, Int32 lStart, Int32 lSamples,
IntPtr lpBuffer, Int32 cbBuffer, Int32 dwFlags,
Int32 dummy1, Int32 dummy2);

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doriandeng

doriandeng

组别:管理员
性别:
积分:1783
帖子:1713

2008-07-04 00:54 | 只看楼主 树型| 收藏| 小中大 4^#

回复: 在AVI文件中隐藏信息

现在创建视频流:

//Create a new video stream
private void CreateStream() {
//describe the stream to create
AVISTREAMINFO strhdr = new AVISTREAMINFO();
strhdr.fccType = this.fccType; //mmioStringToFOURCC("vids", 0)
strhdr.fccHandler = this.fccHandler; //"Microsoft Video 1"
strhdr.dwScale = 1;
strhdr.dwRate = frameRate;
strhdr.dwSuggestedBufferSize = (UInt32)(height * stride);
//use highest quality! Compression destroys the hidden message.
strhdr.dwQuality = 10000;
strhdr.rcFrame.bottom = (UInt32)height;
strhdr.rcFrame.right = (UInt32)width;
strhdr.szName = new UInt16[64];
//create the stream
int result = AVIFileCreateStream(aviFile, out aviStream, ref strhdr);
//define the image format
BITMAPINFOHEADER bi = new BITMAPINFOHEADER();
bi.biSize = (UInt32)Marshal.SizeOf(bi);
bi.biWidth = (Int32)width;
bi.biHeight = (Int32)height;
bi.biPlanes = 1;
bi.biBitCount = 24;
bi.biSizeImage = (UInt32)(this.stride * this.height);
//format the stream
result = Avi.AVIStreamSetFormat(aviStream, 0, ref bi, Marshal.SizeOf(bi));
}

写入帧:

//Create an empty AVI file
public void Open(string fileName, UInt32 frameRate) {
this.frameRate = frameRate;
Avi.AVIFileInit();
int hr = Avi.AVIFileOpen(
ref aviFile, fileName,
OF_WRITE | OF_CREATE, 0);
}
//Add a sample to the stream - for first sample: create the stream
public void AddFrame(Bitmap bmp) {
BitmapData bmpDat = bmp.LockBits(
new Rectangle(0, 0, bmp.Width, bmp.Height),
ImageLockMode.ReadOnly,PixelFormat.Format24bppRgb);
//this is the first frame - get size and create a new stream
if (this.countFrames == 0) {
this.stride = (UInt32)bmpDat.Stride;
this.width = bmp.Width;
this.height = bmp.Height;
CreateStream(); //a method to create a new video stream
}
//add the bitmap to the stream
int result = AVIStreamWrite(aviStream,
countFrames, 1,
bmpDat.Scan0, //pointer to the beginning of the image data
(Int32) (stride * height),
0, 0, 0);
bmp.UnlockBits(bmpDat);
this.countFrames ++;
}
[代码中CryptUtility类的改变]
HideOrExtract() 在前面的版本中一次读入所有载体位图,但现在必须改进了,每次加在一个位图,在加载下一个位图前先释放本位图.当前使用的位图(一个简单的位图或者AVI的一帧)保存在BitmapInfo结构中,通过by ref方式传递
public struct BitmapInfo{
//uncompressed image
public Bitmap bitmap;
//position of the frame in the AVI stream, -1 for non-avi bitmaps
public int aviPosition;
//count of frames in the AVI stream, or 0 for non-avi bitmaps
public int aviCountFrames;
//path and name of the bitmap file
//this file will be deleted later, if aviPosition is 0 or greater
public String sourceFileName;
//how many bytes will be hidden in this image
public long messageBytesToHide;
public void LoadBitmap(String fileName){
bitmap = new Bitmap(fileName);
sourceFileName = fileName;
}
}

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