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); } }
