ScreenBase实现屏幕任意区域的截取

 

 ScreenBase实现屏幕任意区域的截取

//========================================================================
//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: interface for the CScreenBase class.
/**///////////////////////////////////////////////////////////////////////
#ifndef SCREENBASE_H
#define SCREENBASE_H
//-------------------------------------------------------------------

class CScreenBase  
...{
public:
    void CopyScreen();
    void SaveFile(TCHAR *pszPath);
    CScreenBase();
    virtual ~CScreenBase();
    void Initialize(const RECT *prcScr = NULL);

protected:
    void Destroy();
    typedef struct
    ...{
        HDC hDC;                //The DC save the screed DC
        HGDIOBJ hOldSel;        //The old object of save DC
        HBITMAP hBmpSel;        //The selected bitmap
    }SAVEDCINFO,*LPSAVEDCINFO;
    SAVEDCINFO m_SaveDCInfo;

    typedef struct
    ...{
        BYTE *lpBitmapBits;        //Pointer to a variable that receives a pointer to the location of the device-independent bitmap's bit values 
        BITMAPINFO bitMapInfo;    //The savebitmap info
    }SAVEBITMAPINFO,*LPSAVEBITMAPINFO;
    SAVEBITMAPINFO m_SaveBitmapInfo;

    void SaveFile(LPSAVEBITMAPINFO lpSaveBitmapInfo,TCHAR *pszPath);
    void InitializeSaveDC(LPSAVEDCINFO lpSaveDCInfo,LPSAVEBITMAPINFO lpSaveBitmapInfo,const RECT *prcSave);
    void DestroySaveDC(LPSAVEDCINFO lpSaveDCInfo,LPSAVEBITMAPINFO lpSaveBitmapInfo);
    void CopyScreenDC(HDC *pHdcDest,const LPSAVEBITMAPINFO lpSaveBitmapInfo,const RECT *prcSrc);

    RECT m_rcSave;    //The area for saving
    HDC    m_hScrDC;    //The handle DC of screen
};


//--------------------------------------------------------------------------
#endif // !defined SCREENBASE_H

 

/**///////////////////////////////////////////////////////////////////////
// ScreenBase.cpp: implementation of the CScreenBase class.
/**///////////////////////////////////////////////////////////////////////

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

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

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

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

//----------------------------------------------------------------------
//Description:
//    Destroy the save DC
//--------------------------------------------------------------------
void CScreenBase::DestroySaveDC(LPSAVEDCINFO lpSaveDCInfo, LPSAVEBITMAPINFO lpSaveBitmapInfo)
...{
    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:
//    Initialize the save DC
//--------------------------------------------------------------------
void CScreenBase::InitializeSaveDC(LPSAVEDCINFO lpSaveDCInfo, LPSAVEBITMAPINFO lpSaveBitmapInfo,const RECT *prcSave)
...{
 
    //the pointer will save all pixel point's color value
    lpSaveBitmapInfo->lpBitmapBits = NULL;
    

    //creates a memory device context (DC) compatible with the screen device(hScrDC)  
    lpSaveDCInfo->hDC = CreateCompatibleDC(m_hScrDC);


    //Initialise the struct BITMAPINFO for the bimap infomation ，
    //in order to use the function CreateDIBSection on wince os, 
    //each pixel stored by 24 bits(biBitCount=24) and no compressing(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;
   
     //use the function CreateDIBSection and SelectObject in order to get the bimap pointer : lpBitmapBits
    lpSaveDCInfo->hBmpSel = CreateDIBSection(lpSaveDCInfo->hDC, 
                                        &lpSaveBitmapInfo->bitMapInfo, 
                                        DIB_RGB_COLORS, 
                                        ( void  **)&lpSaveBitmapInfo->lpBitmapBits, 
                                        NULL,
                                        0);
    lpSaveDCInfo->hOldSel = SelectObject(lpSaveDCInfo->hDC, lpSaveDCInfo->hBmpSel);


}

//----------------------------------------------------------------------
//Description:
//    Save the bitmap of save dc to the file
//--------------------------------------------------------------------
void  CScreenBase::SaveFile(LPSAVEBITMAPINFO lpSaveBitmapInfo, TCHAR *pszPath)
... {

     int  iWidth = lpSaveBitmapInfo->bitMapInfo.bmiHeader.biWidth;
     int  iHeight = lpSaveBitmapInfo->bitMapInfo.bmiHeader.biHeight;

     //If you only want to get the every pixel color value, 
    //you can begin here and the following part of this function will be unuseful;
    //the following part is in order to write file;

    //Bimap file header in order to write bmp file
    BITMAPFILEHEADER bmBITMAPFILEHEADER;
    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)

    //write into file 
    FILE *mStream = NULL;
    if((mStream = _tfopen(pszPath, TEXT("wb"))))
    ...{  
        //write bitmap file header
        fwrite(&bmBITMAPFILEHEADER, sizeof(BITMAPFILEHEADER), 1, mStream);
        //write bitmap info 
        fwrite(&(lpSaveBitmapInfo->bitMapInfo.bmiHeader), sizeof(BITMAPINFOHEADER), 1, mStream);
        //write bitmap pixels data
        fwrite(lpSaveBitmapInfo->lpBitmapBits, 3*iWidth*iHeight, 1, mStream);
        //close file
        fclose(mStream);
    }
}


//----------------------------------------------------------------------
//Description:
//    Copy the screen DC to the dest DC
//--------------------------------------------------------------------
void  CScreenBase::CopyScreenDC(HDC *pHdcDest, const  LPSAVEBITMAPINFO lpSaveBitmapInfo, const  RECT *prcSrc)
... {
     // copy the screen dc to the memory dc
    BitBlt(*pHdcDest, 0, 0, lpSaveBitmapInfo->bitMapInfo.bmiHeader.biWidth, lpSaveBitmapInfo->bitMapInfo.bmiHeader.biHeight, m_hScrDC, prcSrc->left, prcSrc->top, SRCCOPY);
}


//----------------------------------------------------------------------
//Description:
//    Initialize the instance
//--------------------------------------------------------------------
void  CScreenBase::Initialize( const  RECT *prcScr)
... {
    Destroy();
     //creates a device context for the screen device 
    m_hScrDC = CreateDC(_T("DISPLAY"), NULL, NULL, NULL);
     if (prcScr != NULL)
     ... {
        m_rcSave = *prcScr;
    }
     else
     ... {
         //Get the full window
         int     iWidth = GetDeviceCaps(m_hScrDC, HORZRES);
         int  iHeight = GetDeviceCaps(m_hScrDC, VERTRES);
        m_rcSave.left = 0;
        m_rcSave.top = 0;
        m_rcSave.bottom = iHeight;
        m_rcSave.right = iWidth;
    }
    InitializeSaveDC(&m_SaveDCInfo,&m_SaveBitmapInfo,&m_rcSave);
}


//----------------------------------------------------------------------
//Description:
//    Destroy all the resource
//--------------------------------------------------------------------
void  CScreenBase::Destroy()
... {
     if (m_hScrDC != NULL)
     ... {
        DeleteDC(m_hScrDC);
        m_hScrDC = NULL;
    }
    DestroySaveDC(&m_SaveDCInfo,&m_SaveBitmapInfo);
}


//----------------------------------------------------------------------
//Description:
//    Save the bitmap of screen to the file
//--------------------------------------------------------------------
void  CScreenBase::SaveFile(TCHAR *pszPath)
... {
    SaveFile(&m_SaveBitmapInfo,pszPath);
}

//----------------------------------------------------------------------
//Description:
//    Copy the screen to the save DC
//--------------------------------------------------------------------
void  CScreenBase::CopyScreen()
... {
    CopyScreenDC(&m_SaveDCInfo.hDC,&m_SaveBitmapInfo,&m_rcSave);
}

 

2. 如何截取屏幕

   采用 CScreenBase 类截取全屏非常简单 :
  
   首先声明一个 CScreenBase 类对象 : 

 CScreenBase scrBase;

   接着便是初始化 :

 scrBase.Initialize();

  
   拷贝屏幕图像 :

  scrBase.CopyScreen();

  
   最后 , 把截屏保存到文件中 :

 scrBase.SaveFile(TEXT("Capture.bmp"));

 
   如果是截取屏幕的某个区域 , 需要在初始化的时候确定区域 .
   例如 , 我们需要截取屏幕上以 (20,20) 为起点 , 对角为 (50,60) 的区域 , 只需更改初始化代码即可 :

  RECT rcWnd = ...{20,20,50,60};
  scrBase.Initialize(&rcWnd);

 
  
  
3. 进阶用法 : 将截取的区域直接显示到屏幕

   因为 CScreenBase 类本意是作为一个截图的基本类 , 所以没有封装直接显示到屏幕的方法 . 不过 , 我们可以继承该类 , 然后返回保存区域图片的句柄 , 最后将其显示于屏幕即可 .
  
   派生一个 ScreenPro 类 , 用来返回所需的句柄 .

        class ScreenPro: public CScreenBase
        ...{
            public:
                HDC GetSaveDC()...{return m_SaveDCInfo.hDC;};
                RECT GetSaveRect()...{return m_rcSave;};
        };

   最后我们只需在 WM_PAINT 消息相应函数将保存的区域像素绘制出来即可 :

    //----------------------------------------------------------------------
        //Description:
        //    On message WM_PAINT
        //--------------------------------------------------------------------
        void OnPaint(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
        ...{
            
            if(m_bScrCapture == TRUE)
            ...{
                // 如果已经截屏 , 则将其显示于屏幕上
                
                PAINTSTRUCT ps;
                HDC hdc = BeginPaint(hWnd,&ps);
                
                 // 获取截屏的区域
                RECT rcWnd ;
                rcWnd = m_ScrCapture.GetSaveRect();
                
                 // 获取截屏数据保存的 DC
                HDC hSaveDC = NULL;
                hSaveDC = m_ScrCapture.GetSaveDC();
                
                 // 绘制到屏幕
                BitBlt(hdc,rcWnd.left,rcWnd.top,rcWnd.right,rcWnd.bottom,hSaveDC,0,0,SRCCOPY);    
                EndPaint(hWnd,&ps);
            }
             else
             ... {
                DefWindowProc(hWnd,wMsg,wParam,lParam);
            }
        }