Using Visual C + + to realize image interception of AVI file

AVI file is what we call multimedia files, the so-called AVI image is a video image, the file is a riff description file, which is used to obtain, edit, demo audio, video sequence. The general AVI file contains audio streams and video streams, and some special AVI also contains a control path or MIDI path as an additional data stream.

There are many softwares for playing AVI file now, but most of them can't read one frame image from avi video file and produce BMP format file. The author accumulates some experience in the operation of AVI file in the process of developing project of AVI file, and how to realize the image data of any frame from AVI video stream and store it into BMP file, in which the key is to get the image data of a specific frame from AVI file. For this purpose, I implemented a custom Cavi class using the API functions provided by Windows to manipulate AVI files.

When using API functions to operate AVI files, be sure to use Avifileinit () to initialize the AVI library, the end of the program with Avifileexit () Release AVI library, otherwise the API function can not be used. An example of an AVI file containing true color images is given, in which the cavicreate () function is used to read AVI file information and initialize members of Cavi class, for example, to define the width, height and cavi of each frame image according to AVI file information. The information header structure of each frame image and so on; function aviread (int mframe) is used to read the Mframe frame from an AVI file. The implementation code appears as follows:

Cavi class header file definition; Class Cavi File://AVI classes, processing AVI files { Public int cy;//Image High int cx;//Image Width File://long M_maxframe; BYTE *pdata;//inch stored image data Bitmapinfo *m_pbmi;//bitmap File information header Pavistream Pavi;//avi Flow Pavifile Pfile;//avi file pointer Avifileinfo * PFI; File://AVI Information BOOL aviread (int mframe);//Read mframe frame of AVI file Cavi ()//Standard constructor Cavicreate (CString &string); Initialize the members of an AVI class with a filename Virtual ~cavi (); }; Cavi class file Implementation section; Cavi::cavi () {Avifileinit ()//initializing AVI Library cx=0;//definition image wide, high, etc members cy=0; M_pbmi=null; Pdata=null; file://m_maxFrame=0; Pfi=null; } Cavi::~cavi ()//destructor, release pointer { Avifileclose (pfile); Avifileexit (); if (pdata!=null) Delete PData; Pdata=null; if (m_pbmi!=null) Delete M_pbmi; M_pbmi=null; if (pfi!=null) Delete PFI; Pfi=null; } Cavi::cavicreate (CString &string)/Read File initializes the class { HRESULT hr; Pfi=new Avifileinfo; hr = AVIFileOpen (&pfile,//returned file pointer string,//file name Of_read,//mode to open file with NULL); Hr= Avifileinfo (pfile, file://get AVI information, into the PFI Pfi sizeof (Avifileinfo) ); cx=pfi->dwwidth;//image wide and high cy=pfi->dwheight; Hr=avifilegetstream (//To turn AVI into a video stream Pfile &pavi, Streamtypevideo, 0//long LParam ); M_pbmi=new bitmapinfo;//define BMP information Header m_pbmi->bmiheader.bibitcount=24; m_pbmi->bmiheader.biclrimportant=0; m_pbmi->bmiheader.biclrused=0; m_pbmi->bmiheader.bicompression=bi_rgb; m_pbmi->bmiheader.biheight=cy; m_pbmi->bmiheader.biwidth=cx; m_pbmi->bmiheader.biplanes=1; M_pbmi->bmiheader.bisize=sizeof (Bitmapinfoheader); m_pbmi->bmiheader.bixpelspermeter=0; m_pbmi->bmiheader.biypelspermeter=0; m_pbmi->bmiheader.bisizeimage=cx*cy*3; Pdata= (byte*) New char[cx*cy*3];//defines a buffer based on the information of BMP images in avi } BOOL cavi::aviread (int mframe)//To read the M frame data of AVI file into pdata buffer { HRESULT hr; Hr= Avistreamread (Pavi, Mframe, 1, PData, Cx*cy*3, Null Null ); if (hr==0) return TRUE; Else return FALSE; }

The API functions involved in the above Cavi class implementation section refer to the MSDN provided by Microsoft. Cavi class of pdata buffer storage AVI file in the specific frame image data, and Cavi class of M_PBMI for BMP image file information structure, at this time can be based on the size of the image to define BMP image file header structure, the storage of BMP files, due to the length of the reasons, I do not speak more , interested readers can see the author's flops "Visual c++6.0 development Grayscale Bitmap Processing" (Tenkine software column published in 2001.9.10), which describes how to access BMP files. The above procedures in Windows2000, Visual c++6.0 Environment smoothly compiled through, normal operation.