怎么样使用ScreenBase实现截取屏幕任意区域？

//========================================================================
//TITLE:
// ScreenBase实现屏幕任意区域的截取
//AUTHOR:
// norains
//DATE:
// Tuesday 16-January -2007
//Environment:
//EVC4.0 + Standard SDK
//========================================================================

1.ScreenBase 源码

ScreenBase为自己写代码方便而封装的一个API类,该类的的主要功能是截取屏幕任意区域的图像,并将之保存为BMP文件.

源代码如下:

/**///////////////////////////////////////////////////////////////////////
//ScreenBase.h:interfacefortheCScreenBaseclass.
/**///////////////////////////////////////////////////////////////////////
#ifndefSCREENBASE_H
#defineSCREENBASE_H
//-------------------------------------------------------------------

classCScreenBase
...{
public:
voidCopyScreen();
voidSaveFile(TCHAR*pszPath);
CScreenBase();
virtual~CScreenBase();
voidInitialize(constRECT*prcScr=NULL);

protected:
voidDestroy();
typedefstruct
...{
HDChDC;//TheDCsavethescreedDC
HGDIOBJhOldSel;//TheoldobjectofsaveDC
HBITMAPhBmpSel;//Theselectedbitmap
}SAVEDCINFO,*LPSAVEDCINFO;
SAVEDCINFOm_SaveDCInfo;

typedefstruct
...{
BYTE*lpBitmapBits;//Pointertoavariablethatreceivesapointertothelocationofthedevice-independentbitmap'sbitvalues
BITMAPINFObitMapInfo;//Thesavebitmapinfo
}SAVEBITMAPINFO,*LPSAVEBITMAPINFO;
SAVEBITMAPINFOm_SaveBitmapInfo;

voidSaveFile(LPSAVEBITMAPINFOlpSaveBitmapInfo,TCHAR*pszPath);
voidInitializeSaveDC(LPSAVEDCINFOlpSaveDCInfo,LPSAVEBITMAPINFOlpSaveBitmapInfo,constRECT*prcSave);
voidDestroySaveDC(LPSAVEDCINFOlpSaveDCInfo,LPSAVEBITMAPINFOlpSaveBitmapInfo);
voidCopyScreenDC(HDC*pHdcDest,constLPSAVEBITMAPINFOlpSaveBitmapInfo,constRECT*prcSrc);

RECTm_rcSave;//Theareaforsaving
HDCm_hScrDC;//ThehandleDCofscreen
};


//--------------------------------------------------------------------------
#endif//!definedSCREENBASE_H

/**///////////////////////////////////////////////////////////////////////
//ScreenBase.cpp:implementationoftheCScreenBaseclass.
/**///////////////////////////////////////////////////////////////////////

#include"stdafx.h"
#include"ScreenBase.h"

/**///////////////////////////////////////////////////////////////////////
//Construction/Destruction
/**///////////////////////////////////////////////////////////////////////

CScreenBase::CScreenBase()
...{
memset(&m_rcSave,0,sizeof(m_rcSave));
m_hScrDC=NULL;
}

CScreenBase::~CScreenBase()
...{
Destroy();
}

//----------------------------------------------------------------------
//Description:
//DestroythesaveDC
//--------------------------------------------------------------------
voidCScreenBase::DestroySaveDC(LPSAVEDCINFOlpSaveDCInfo,LPSAVEBITMAPINFOlpSaveBitmapInfo)
...{
if(lpSaveDCInfo->hDC!=NULL&&lpSaveDCInfo->hOldSel!=NULL)
...{
SelectObject(lpSaveDCInfo->hDC,lpSaveDCInfo->hOldSel);
}

if(lpSaveDCInfo->hDC!=NULL)
...{
DeleteDC(lpSaveDCInfo->hDC);
}

if(lpSaveDCInfo->hBmpSel!=NULL)
...{
DeleteObject(lpSaveDCInfo->hBmpSel);
}

memset(lpSaveDCInfo,0,sizeof(SAVEDCINFO));
memset(lpSaveBitmapInfo,0,sizeof(SAVEBITMAPINFO));
}

//----------------------------------------------------------------------
//Description:
//InitializethesaveDC
//--------------------------------------------------------------------
voidCScreenBase::InitializeSaveDC(LPSAVEDCINFOlpSaveDCInfo,LPSAVEBITMAPINFOlpSaveBitmapInfo,constRECT*prcSave)
...{

//thepointerwillsaveallpixelpoint'scolorvalue
lpSaveBitmapInfo->lpBitmapBits=NULL;


//createsamemorydevicecontext(DC)compatiblewiththescreendevice(hScrDC)
lpSaveDCInfo->hDC=CreateCompatibleDC(m_hScrDC);


//InitialisethestructBITMAPINFOforthebimapinfomation，
//inordertousethefunctionCreateDIBSectiononwinceos,
//eachpixelstoredby24bits(biBitCount=24)andnocompressing(biCompression=0)
ZeroMemory(&m_SaveBitmapInfo.bitMapInfo,sizeof(BITMAPINFO));
lpSaveBitmapInfo->bitMapInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
lpSaveBitmapInfo->bitMapInfo.bmiHeader.biWidth=prcSave->right-prcSave->left;
lpSaveBitmapInfo->bitMapInfo.bmiHeader.biHeight=prcSave->bottom-prcSave->top;
lpSaveBitmapInfo->bitMapInfo.bmiHeader.biPlanes=1;
lpSaveBitmapInfo->bitMapInfo.bmiHeader.biBitCount=24;

//usethefunctionCreateDIBSectionandSelectObjectinordertogetthebimappointer:lpBitmapBits
lpSaveDCInfo->hBmpSel=CreateDIBSection(lpSaveDCInfo->hDC,
&lpSaveBitmapInfo->bitMapInfo,
DIB_RGB_COLORS,
(void**)&lpSaveBitmapInfo->lpBitmapBits,
NULL,
0);
lpSaveDCInfo->hOldSel=SelectObject(lpSaveDCInfo->hDC,lpSaveDCInfo->hBmpSel);


}

//----------------------------------------------------------------------
//Description:
//Savethebitmapofsavedctothefile
//--------------------------------------------------------------------
voidCScreenBase::SaveFile(LPSAVEBITMAPINFOlpSaveBitmapInfo,TCHAR*pszPath)
...{

intiWidth=lpSaveBitmapInfo->bitMapInfo.bmiHeader.biWidth;
intiHeight=lpSaveBitmapInfo->bitMapInfo.bmiHeader.biHeight;

//Ifyouonlywanttogettheeverypixelcolorvalue,
//youcanbeginhereandthefollowingpartofthisfunctionwillbeunuseful;
//thefollowingpartisinordertowritefile;

//Bimapfileheaderinordertowritebmpfile
BITMAPFILEHEADERbmBITMAPFILEHEADER;
ZeroMemory(&bmBITMAPFILEHEADER,sizeof(BITMAPFILEHEADER));
bmBITMAPFILEHEADER.bfType=0x4d42;//bmp
bmBITMAPFILEHEADER.bfOffBits=sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);
bmBITMAPFILEHEADER.bfSize=bmBITMAPFILEHEADER.bfOffBits+((iWidth*iHeight)*3);/**////norains:3=(24/8)

//writeintofile
FILE*mStream=NULL;
if((mStream=_tfopen(pszPath,TEXT("wb"))))
...{
//writebitmapfileheader
fwrite(&bmBITMAPFILEHEADER,sizeof(BITMAPFILEHEADER),1,mStream);
//writebitmapinfo
fwrite(&(lpSaveBitmapInfo->bitMapInfo.bmiHeader),sizeof(BITMAPINFOHEADER),1,mStream);
//writebitmappixelsdata
fwrite(lpSaveBitmapInfo->lpBitmapBits,3*iWidth*iHeight,1,mStream);
//closefile
fclose(mStream);
}
}


//----------------------------------------------------------------------
//Description:
//CopythescreenDCtothedestDC
//--------------------------------------------------------------------
voidCScreenBase::CopyScreenDC(HDC*pHdcDest,constLPSAVEBITMAPINFOlpSaveBitmapInfo,constRECT*prcSrc)
...{
//copythescreendctothememorydc
BitBlt(*pHdcDest,0,0,lpSaveBitmapInfo->bitMapInfo.bmiHeader.biWidth,lpSaveBitmapInfo->bitMapInfo.bmiHeader.biHeight,m_hScrDC,prcSrc->left,prcSrc->top,SRCCOPY);
}


//----------------------------------------------------------------------
//Description:
//Initializetheinstance
//--------------------------------------------------------------------
voidCScreenBase::Initialize(const