用Visual C++设计屏幕抓图程序
【打印文章】
在Windows操作系统中，当用户按下"PrintScreen"按钮后，Windows自动将当前屏幕的图像拷贝到系统剪贴板中，这时可以通过"画笔"这个小程序将剪贴板中的内容保存成图像文件，可以看出，如果需要将当前屏幕保存下来还是比较麻烦的，能否可以自己编写一个应用程序，自动将当前屏幕的内容保存到一个图像文件中去呢？这个答案是肯定的，本实例应用程序就是利用通用的热键管理DLL库实现的热键功能，在收到热键通知后截取屏幕的内容并保存到bmp文件中。例如我们设置图片保存路径为c：\，热键为F9 + Control，然后按Change按钮设置好热键，那么当我们按下CTRL+F9后，当前界面将以BMP图像文件的格式被保存在C：\目录下。
一、实现方法
热键管理DLL实际上是一个键盘钩子，由它来监视系统的键盘事件。如果有和程序登记符合的按键组合就通知该程序的窗口。为了应用方便，本实例把它做成了一个标准的管理库来为其它的程序通过热键服务，它有两个输出函数：AddHotkey（）和DeleteHotkey（），程序只需要调用这两个函数就可以了，如果编译之后不用改变热键，则只需要AddHotkey就可以了。DLL中的所有的全局变量都放在一个共享段中，定义如下：
#pragma data_seg("shareddata")
HHOOK hHook =NULL; //钩子句柄
UINT nHookCount =0; //挂接的程序数目
static UCHAR HotKey[MAX_KEY] = {0}; //热键虚拟键码
static UCHAR HotKeyMask[MAX_KEY] = {0}; //组合掩码, control=4,alt=2,shift=1
static HWND hCallWnd[MAX_KEY] = {0}; //window handle associated with hotkey
static int KeyCount =0;
static UCHAR MaskBits =0; //00000 Ctrl=4 & Alt=2 & Shift=1
#pragma data_seg()
关于共享段，有几点重要的说明：一是必须在链接选项里指定该段为共享：一种方法是在project->settings->link->object/library中加上/section:shareddata,rws；第二种方法是在def文件的sections里加上一句shareddata read write shared；第三种指定共享段的方法在程序里加上一句#pragma comment(linker,"section:shareddata,rws")。二是所有的变量必须初始化，否则链接程序会把它放到普通数据段。三是如果不初始化变量，需要在段外用"__declspec(allocate("shareddata")) 变量类型 变量名"的方式定义。
DLL中的两个输出函数分别用来添加/删除热键，函数代码如下：
BOOL __declspec(dllexport) __stdcall AddHotkey(HWND hWnd,UCHAR
cKey,UCHAR cMask)
{
BOOL bAdded=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==0){
hCallWnd[index]=hWnd;
HotKey[index]=cKey;
HotKeyMask[index]=cMask;
bAdded=TRUE;
KeyCount++;
break;
}
}
return bAdded;
}
//删除热键
BOOL __declspec(dllexport) __stdcall DeleteHotkey(HWND hWnd,
UCHAR cKey,UCHAR cMask)
{
BOOL bRemoved=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==hWnd){
if(HotKey[index]==cKey&&HotKeyMask[index]==cMask){
hCallWnd[index]=NULL;
HotKey[index]=0;
HotKeyMask[index]=0;
bRemoved=TRUE;
KeyCount--;
break;
}
}
}
return bRemoved;
}
DLL中的钩子函数如下：
LRESULT CALLBACK KeyboardProc(int nCode,WPARAM wParam,LPARAM lParam)
{
BOOL bProcessed=FALSE;
if(HC_ACTION==nCode)
{
if((lParam&0xc0000000)==0xc0000000){// 有键松开
switch(wParam)
{
case VK_MENU:
MaskBits&=~ALTBIT;
break;
case VK_CONTROL:
MaskBits&=~CTRLBIT;
break;
case VK_SHIFT:
MaskBits&=~SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYUP);
bProcessed=TRUE;
}
}
}
else if((lParam&0xc000ffff)==1){ //有键按下
switch(wParam)
{
case VK_MENU:
MaskBits|=ALTBIT;
break;
case VK_CONTROL:
MaskBits|=CTRLBIT;
break;
case VK_SHIFT:
MaskBits|=SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYDOWN);
bProcessed=TRUE;
}
}
}
if(!bProcessed){ //一般按键事件，为监视键盘的程序留出余地
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==0)&&(HotKeyMask[index]==0))
SendMessage(hCallWnd[index],WM_HOTKEY,WM_HOTKEY,lParam);
//lParam的意义可看MSDN中WM_KEYDOWN部分
}
}
}
return CallNextHookEx( hHook, nCode, wParam, lParam );
}
抓图程序是一个基于对话框的程序，它在建立对话框的时候调用前面的DLL，登记热键，因此需要将hook.lib添加到工程里，在程序里给出两个DLL函数的定义，也可以写个头文件，再包含进来以下代码：
BOOL __declspec(dllexport)__stdcall AddHotkey(HWND,UCHAR key,UCHAR mask);
BOOL __declspec(dllexport)__stdcall DeleteHotkey(HWND,UCHAR key,UCHAR mask);
为了添加应用程序对热键通知事件的响应，程序中用的办法是重载WindowProc（）函数，该函数代码如下：
LRESULT CCaptureDlg::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
if(message==WM_HOTKEY&&lParam==WM_KEYDOWN)
{ //lParam表示是按下还是松开，如果有多个热键，由wParam来区分
SaveBmp();
return FALSE;
}
…… //其它处理及默认处理
}
将屏幕图像保存到BMP文件中的任务是由函数SaveBmp（）来完成的，具体实现参见代码部分。另外为了顺利实现屏幕抓图，程序中还实现了"托盘"功能，由于这一部分本书在实例中已经专门介绍过了，所以不再赘述，读者朋友可以参考相关实例。
最后需要提醒读者朋友们注意的是，源程序的编译与使用时要先编译hook.dll并将其放在系统目录（win2000/NT是system32，98/ME是system），然后编译对话框程序运行即可。
二、编程步骤
1、 启动Visual C++，生成一个DLL项目和一个基于对话框的应用程序项目，并将两个项目分别命名为"Hook"和"Capture"；
2、 在"Hook"项目中导出AddHotkey（）、DeleteHotkey（）函数；
3、 在"Capture"项目中按照图一所示设置对话框的界面，具体设置参见代码部分；
4、 使用Class Wizard在"Capture"项目中添加按钮的鼠标单击消息响应函数，并重载对话框的WindowProc（）函数；
5、 添加代码，编译运行程序。
三、程序代码
/////////////////////////////////////////////////////////// Hook.h : main header file for the HOOK DLL
#if !defined(AFX_HOOK_H__AEBFF705_C93A_11D5_B7D6_0080C82BE86B__INCLUDED_)
#define AFX_HOOK_H__AEBFF705_C93A_11D5_B7D6_0080C82BE86B__INCLUDED_
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000
#ifndef __AFXWIN_H__
#error include ''stdafx.h'' before including this file for PCH
#endif
#include "resource.h" // main symbols
class CHookApp : public CWinApp
{
public:
CHookApp();
// Overrides
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CHookApp)
public:
virtual BOOL InitInstance();
virtual int ExitInstance();
//}}AFX_VIRTUAL
//{{AFX_MSG(CHookApp)
// NOTE - the ClassWizard will add and remove member functions here.
// DO NOT EDIT what you see in these blocks of generated code !
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
LRESULT CALLBACK KeyboardProc(int nCode,WPARAM wParam, LPARAM lParam);
BOOL __declspec(dllexport)__stdcall AddHotkey(HWND,UCHAR key,UCHAR mask);
BOOL __declspec(dllexport)__stdcall DeleteHotkey(HWND,UCHAR key,UCHAR mask);
BOOL InitHotkey();
BOOL UnInit();
#endif
////////// Hook.cpp : Defines the initialization routines for the DLL.
#include "stdafx.h"
#include "hook.h"
#include <windowsx.h>
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
#define MAX_KEY 100
#define CTRLBIT 0x04
#define ALTBIT 0x02
#define SHIFTBIT 0x01
#pragma data_seg("shareddata")
HHOOK hHook =NULL;
UINT nHookCount =0;
static UCHAR HotKey[MAX_KEY] = {0}; //hotkey
static UCHAR HotKeyMask[MAX_KEY] = {0}; //flag for hotkey, value is VK_CONTRL or VK_NEMU or VK_SHIFT
static HWND hCallWnd[MAX_KEY] = {0}; //window associated with hotkey
static int KeyCount =0;
static UCHAR MaskBits =0; //00000 Ctrl Alt Shift
#pragma data_seg()
HINSTANCE hins;
void VerifyWindow();
BEGIN_MESSAGE_MAP(CHookApp, CWinApp)
//{{AFX_MSG_MAP(CHookApp)
// NOTE - the ClassWizard will add and remove mapping macros here.
// DO NOT EDIT what you see in these blocks of generated code!
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
CHookApp::CHookApp()
{
// TODO: add construction code here,
// Place all significant initialization in InitInstance
}
CHookApp theApp;
LRESULT CALLBACK KeyboardProc(int nCode,WPARAM wParam,LPARAM lParam)
{
BOOL bProcessed=FALSE;
if(HC_ACTION==nCode)
{
if((lParam&0xc0000000)==0xc0000000){// Key up
switch(wParam)
{
case VK_MENU:
MaskBits&=~ALTBIT;
break;
case VK_CONTROL:
MaskBits&=~CTRLBIT;
break;
case VK_SHIFT:
MaskBits&=~SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYUP);
bProcessed=TRUE;
}
}
}
else if((lParam&0xc000ffff)==1){ //Key down
switch(wParam)
{
case VK_MENU:
MaskBits|=ALTBIT;
break;
case VK_CONTROL:
MaskBits|=CTRLBIT;
break;
case VK_SHIFT:
MaskBits|=SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++)
{
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYDOWN);
bProcessed=TRUE;
}
}
}
if(!bProcessed){
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==0)&&(HotKeyMask[index]==0))
SendMessage(hCallWnd[index],WM_HOTKEY,WM_HOTKEY,lParam);
}
}
}
return CallNextHookEx( hHook, nCode, wParam, lParam );
}
BOOL InitHotkey()
{
if(hHook!=NULL){
nHookCount++;
return TRUE;
}
else
hHook=SetWindowsHookEx(WH_KEYBOARD,(HOOKPROC)KeyboardProc,hins,0);
if(hHook!=NULL)
nHookCount++;
return (hHook!=NULL);
}
BOOL UnInit()
{
if(nHookCount>1){
nHookCount--;
return TRUE;
}
BOOL unhooked = UnhookWindowsHookEx(hHook);
if(unhooked==TRUE){
nHookCount=0;
hHook=NULL;
}
return unhooked;
}
BOOL __declspec(dllexport) __stdcall AddHotkey(HWND hWnd,UCHAR cKey,UCHAR cMask)
{
BOOL bAdded=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==0){
hCallWnd[index]=hWnd;
HotKey[index]=cKey;
HotKeyMask[index]=cMask;
bAdded=TRUE;
KeyCount++;
break;
}
}
return bAdded;
}
BOOL __declspec(dllexport) __stdcall DeleteHotkey(HWND hWnd,UCHAR cKey,UCHAR cMask)
{
BOOL bRemoved=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==hWnd){
if(HotKey[index]==cKey&&HotKeyMask[index]==cMask){
hCallWnd[index]=NULL;
HotKey[index]=0;
HotKeyMask[index]=0;
bRemoved=TRUE;
KeyCount--;
break;
}
}
}
return bRemoved;
}
void VerifyWindow()
{
for(int i=0;i<MAX_KEY;i++){
if(hCallWnd[i]!=NULL){
if(!IsWindow(hCallWnd[i])){
hCallWnd[i]=NULL;
HotKey[i]=0;
HotKeyMask[i]=0;
KeyCount--;
}
}
}
}
BOOL CHookApp::InitInstance()
{
AFX_MANAGE_STATE(AfxGetStaticModuleState());
hins=AfxGetInstanceHandle();
InitHotkey();
return CWinApp::InitInstance();
}
int CHookApp::ExitInstance()
{
VerifyWindow();
UnInit();
return CWinApp::ExitInstance();
}
////////////////////////////////////////////////////////////////////// CaptureDlg.h : header file
#if !defined(AFX_CAPTUREDLG_H__97B51708_C928_11D5_B7D6_0080C82BE86B__INCLUDED_)
#define AFX_CAPTUREDLG_H__97B51708_C928_11D5_B7D6_0080C82BE86B__INCLUDED_
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000
class CCaptureDlg : public CDialog
{
// Construction
public:
BOOL bTray;
BOOL bRegistered;
BOOL RegisterHotkey();
UCHAR cKey;
UCHAR cMask;
void DeleteIcon();
void AddIcon();
UINT nCount;
void SaveBmp();
CCaptureDlg(CWnd* pParent = NULL); // standard constructor
// Dialog Data
//{{AFX_DATA(CCaptureDlg)
enum { IDD = IDD_CAPTURE_DIALOG };
CComboBox m_Key;
BOOL m_bControl;
BOOL m_bAlt;
BOOL m_bShift;
CString m_Path;
CString m_Number;
//}}AFX_DATA
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CCaptureDlg)
public:
virtual BOOL PreTranslateMessage(MSG* pMsg);
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
virtual LRESULT WindowProc(UINT message, WPARAM wParam, LPARAM lParam);
//}}AFX_VIRTUAL
// Implementation
protected:
HICON m_hIcon;
// Generated message map functions
//{{AFX_MSG(CCaptureDlg)
virtual BOOL OnInitDialog();
afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
afx_msg void OnPaint();
afx_msg HCURSOR OnQueryDragIcon();
virtual void OnCancel();
afx_msg void OnAbout();
afx_msg void OnBrowse();
afx_msg void OnChange();
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
#endif
////////////////////// CaptureDlg.cpp : implementation file
#include "stdafx.h"
#include "Capture.h"
#include "CaptureDlg.h"
#include <windowsx.h>
#pragma comment(lib,"hook.lib")
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
#define IDM_SHELL WM_USER+1
BOOL __declspec(dllexport)__stdcall AddHotkey(HWND,UCHAR key,UCHAR mask);
BOOL __declspec(dllexport)__stdcall DeleteHotkey(HWND,UCHAR key,UCHAR mask);
UCHAR Key_Table[]={0x78,0x79,0x7a,0x7b,0x6a,0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39};
class CAboutDlg : public CDialog
{
public:
CAboutDlg();
// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL
// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}
void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
CCaptureDlg::CCaptureDlg(CWnd* pParent /*=NULL*/)
: CDialog(CCaptureDlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CCaptureDlg)
m_bControl = FALSE;
m_bAlt = FALSE;
m_bShift = FALSE;
m_Path = _T("c:");
m_Number = _T("0 picture captured.");
nCount=0;
bRegistered=FALSE;
bTray=FALSE;
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}
void CCaptureDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CCaptureDlg)
DDX_Control(pDX, IDC_KEY, m_Key);
DDX_Check(pDX, IDC_CONTROL, m_bControl);
DDX_Check(pDX, IDC_ALT, m_bAlt);
DDX_Check(pDX, IDC_SHIFT, m_bShift);
DDX_Text(pDX, IDC_PATH, m_Path);
DDX_Text(pDX, IDC_NUMBER, m_Number);
//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CCaptureDlg, CDialog)
//{{AFX_MSG_MAP(CCaptureDlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_BN_CLICKED(ID_ABOUT, OnAbout)
ON_BN_CLICKED(IDC_BROWSE, OnBrowse)
ON_BN_CLICKED(ID_CHANGE, OnChange)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
BOOL CCaptureDlg::OnInitDialog()
{
CDialog::OnInitDialog();
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000);
CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
}
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon
m_Key.SetCurSel(0);
RegisterHotkey();
CMenu* pMenu=GetSystemMenu(FALSE);
pMenu->DeleteMenu(SC_MAXIMIZE,MF_BYCOMMAND);
pMenu->DeleteMenu(SC_SIZE,MF_BYCOMMAND);
pMenu->DeleteMenu(SC_RESTORE,MF_BYCOMMAND);
return TRUE; // return TRUE unless you set the focus to a control
}
void CCaptureDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}
void CCaptureDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting
SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);
// Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;
// Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}
HCURSOR CCaptureDlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}
void CCaptureDlg::OnCancel()
{
if(bTray)
DeleteIcon();
CDialog::OnCancel();
}
void CCaptureDlg::OnAbout()
{
CAboutDlg dlg;
dlg.DoModal();
}
void CCaptureDlg::OnBrowse()
{
CString str;
BROWSEINFO bi;
char name[MAX_PATH];
ZeroMemory(&bi,sizeof(BROWSEINFO));
bi.hwndOwner=GetSafeHwnd();
bi.pszDisplayName=name;
bi.lpszTitle="Select folder";
bi.ulFlags=BIF_RETURNONLYFSDIRS;
LPITEMIDLIST idl=SHBrowseForFolder(&bi);
if(idl==NULL)
return;
SHGetPathFromIDList(idl,str.GetBuffer(MAX_PATH));
str.ReleaseBuffer();
m_Path=str;
if(str.GetAt(str.GetLength()-1)!='''')
m_Path+="";
UpdateData(FALSE);
}
void CCaptureDlg::SaveBmp()
{
CDC dc;
dc.CreateDC("DISPLAY",NULL,NULL,NULL);
CBitmap bm;
int Width=GetSystemMetrics(SM_CXSCREEN);
int Height=GetSystemMetrics(SM_CYSCREEN);
bm.CreateCompatibleBitmap(&dc,Width,Height);
CDC tdc;
tdc.CreateCompatibleDC(&dc);
CBitmap*pOld=tdc.SelectObject(&bm);
tdc.BitBlt(0,0,Width,Height,&dc,0,0,SRCCOPY);
tdc.SelectObject(pOld);
BITMAP btm;
bm.GetBitmap(&btm);
DWORD size=btm.bmWidthBytes*btm.bmHeight;
LPSTR lpData=(LPSTR)GlobalAllocPtr(GPTR,size);
BITMAPINFOHEADER bih;
bih.biBitCount=btm.bmBitsPixel;
bih.biClrImportant=0;
bih.biClrUsed=0;
bih.biCompression=0;
bih.biHeight=btm.bmHeight;
bih.biPlanes=1;
bih.biSize=sizeof(BITMAPINFOHEADER);
bih.biSizeImage=size;
bih.biWidth=btm.bmWidth;
bih.biXPelsPerMeter=0;
bih.biYPelsPerMeter=0;
GetDIBits(dc,bm,0,bih.biHeight,lpData,(BITMAPINFO*)&bih,DIB_RGB_COLORS);
static int filecount=0;
CString name;
name.Format("pict%04d.bmp",filecount++);
name=m_Path+name;
BITMAPFILEHEADER bfh;
bfh.bfReserved1=bfh.bfReserved2=0;
bfh.bfType=((WORD)(''M''<< 8)|''B'');
bfh.bfSize=54+size;
bfh.bfOffBits=54;
CFile bf;
if(bf.Open(name,CFile::modeCreate|CFile::modeWrite)){
bf.WriteHuge(&bfh,sizeof(BITMAPFILEHEADER));
bf.WriteHuge(&bih,sizeof(BITMAPINFOHEADER));
bf.WriteHuge(lpData,size);
bf.Close();
nCount++;
}
GlobalFreePtr(lpData);
if(nCount==1)
m_Number.Format("%d picture captured.",nCount);
else
m_Number.Format("%d pictures captured.",nCount);
UpdateData(FALSE);
}
BOOL CCaptureDlg::PreTranslateMessage(MSG* pMsg)
{
if(pMsg -> message == WM_KEYDOWN)
{
if(pMsg -> wParam == VK_ESCAPE)
return TRUE;
if(pMsg -> wParam == VK_RETURN)
return TRUE;
}
return CDialog::PreTranslateMessage(pMsg);
}
LRESULT CCaptureDlg::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
if(message==WM_HOTKEY&&lParam==WM_KEYDOWN){
SaveBmp();
return FALSE;
}
if(message==IDM_SHELL&&lParam==WM_RBUTTONUP){
CMenu pop;
pop.LoadMenu(MAKEINTRESOURCE(IDR_MENU1));
CMenu*pMenu=pop.GetSubMenu(0);
pMenu->SetDefaultItem(ID_EXITICON);
CPoint pt;
GetCursorPos(&pt);
int id=pMenu->TrackPopupMenu(TPM_RIGHTALIGN|TPM_NONOTIFY|TPM_RETURNCMD|TPM_LEFTBUTTON,pt.x,pt.y,this);
if(id==ID_EXITICON)
DeleteIcon();
else if(id==ID_EXIT)
OnCancel();
return FALSE;
}
LRESULT res= CDialog::WindowProc(message, wParam, lParam);
if(message==WM_SYSCOMMAND&&wParam==SC_MINIMIZE)
AddIcon();
return res;
}
void CCaptureDlg::AddIcon()
{
NOTIFYICONDATA data;
data.cbSize=sizeof(NOTIFYICONDATA);
CString tip;
tip.LoadString(IDS_ICONTIP);
data.hIcon=GetIcon(0);
data.hWnd=GetSafeHwnd();
strcpy(data.szTip,tip);
data.uCallbackMessage=IDM_SHELL;
data.uFlags=NIF_ICON|NIF_MESSAGE |NIF_TIP ;
data.uID=98;
Shell_NotifyIcon(NIM_ADD,&data);
ShowWindow(SW_HIDE);
bTray=TRUE;
}
void CCaptureDlg::DeleteIcon()
{
NOTIFYICONDATA data;
data.cbSize=sizeof(NOTIFYICONDATA);
data.hWnd=GetSafeHwnd();
data.uID=98;
Shell_NotifyIcon(NIM_DELETE,&data);
ShowWindow(SW_SHOW);
SetForegroundWindow();
ShowWindow(SW_SHOWNORMAL);
bTray=FALSE;
}
void CCaptureDlg::OnChange()
{
RegisterHotkey();
}
BOOL CCaptureDlg::RegisterHotkey()
{
UpdateData();
UCHAR mask=0;
UCHAR key=0;
if(m_bControl)
mask|=4;
if(m_bAlt)
mask|=2;
if(m_bShift)
mask|=1;
key=Key_Table[m_Key.GetCurSel()];
if(bRegistered){
DeleteHotkey(GetSafeHwnd(),cKey,cMask);
bRegistered=FALSE;
}
cMask=mask;
cKey=key;
bRegistered=AddHotkey(GetSafeHwnd(),cKey,cMask);
return bRegistered;
}
四、小结
本实例通过一个钩子DLL实现了屏幕抓图的功能，它有一个缺陷，那就是只能保存整个屏幕图像，不过读者朋友可以在此基础上，实现屏幕任意区域的抓图功能，具体方法不再赘述，实现起来很容易的了，呵呵。
一、实现方法
热键管理DLL实际上是一个键盘钩子，由它来监视系统的键盘事件。如果有和程序登记符合的按键组合就通知该程序的窗口。为了应用方便，本实例把它做成了一个标准的管理库来为其它的程序通过热键服务，它有两个输出函数：AddHotkey（）和DeleteHotkey（），程序只需要调用这两个函数就可以了，如果编译之后不用改变热键，则只需要AddHotkey就可以了。DLL中的所有的全局变量都放在一个共享段中，定义如下：
#pragma data_seg("shareddata")
HHOOK hHook =NULL; //钩子句柄
UINT nHookCount =0; //挂接的程序数目
static UCHAR HotKey[MAX_KEY] = {0}; //热键虚拟键码
static UCHAR HotKeyMask[MAX_KEY] = {0}; //组合掩码, control=4,alt=2,shift=1
static HWND hCallWnd[MAX_KEY] = {0}; //window handle associated with hotkey
static int KeyCount =0;
static UCHAR MaskBits =0; //00000 Ctrl=4 & Alt=2 & Shift=1
#pragma data_seg()
关于共享段，有几点重要的说明：一是必须在链接选项里指定该段为共享：一种方法是在project->settings->link->object/library中加上/section:shareddata,rws；第二种方法是在def文件的sections里加上一句shareddata read write shared；第三种指定共享段的方法在程序里加上一句#pragma comment(linker,"section:shareddata,rws")。二是所有的变量必须初始化，否则链接程序会把它放到普通数据段。三是如果不初始化变量，需要在段外用"__declspec(allocate("shareddata")) 变量类型 变量名"的方式定义。
DLL中的两个输出函数分别用来添加/删除热键，函数代码如下：
BOOL __declspec(dllexport) __stdcall AddHotkey(HWND hWnd,UCHAR
cKey,UCHAR cMask)
{
BOOL bAdded=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==0){
hCallWnd[index]=hWnd;
HotKey[index]=cKey;
HotKeyMask[index]=cMask;
bAdded=TRUE;
KeyCount++;
break;
}
}
return bAdded;
}
//删除热键
BOOL __declspec(dllexport) __stdcall DeleteHotkey(HWND hWnd,
UCHAR cKey,UCHAR cMask)
{
BOOL bRemoved=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==hWnd){
if(HotKey[index]==cKey&&HotKeyMask[index]==cMask){
hCallWnd[index]=NULL;
HotKey[index]=0;
HotKeyMask[index]=0;
bRemoved=TRUE;
KeyCount--;
break;
}
}
}
return bRemoved;
}
DLL中的钩子函数如下：
LRESULT CALLBACK KeyboardProc(int nCode,WPARAM wParam,LPARAM lParam)
{
BOOL bProcessed=FALSE;
if(HC_ACTION==nCode)
{
if((lParam&0xc0000000)==0xc0000000){// 有键松开
switch(wParam)
{
case VK_MENU:
MaskBits&=~ALTBIT;
break;
case VK_CONTROL:
MaskBits&=~CTRLBIT;
break;
case VK_SHIFT:
MaskBits&=~SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYUP);
bProcessed=TRUE;
}
}
}
else if((lParam&0xc000ffff)==1){ //有键按下
switch(wParam)
{
case VK_MENU:
MaskBits|=ALTBIT;
break;
case VK_CONTROL:
MaskBits|=CTRLBIT;
break;
case VK_SHIFT:
MaskBits|=SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYDOWN);
bProcessed=TRUE;
}
}
}
if(!bProcessed){ //一般按键事件，为监视键盘的程序留出余地
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==0)&&(HotKeyMask[index]==0))
SendMessage(hCallWnd[index],WM_HOTKEY,WM_HOTKEY,lParam);
//lParam的意义可看MSDN中WM_KEYDOWN部分
}
}
}
return CallNextHookEx( hHook, nCode, wParam, lParam );
}
抓图程序是一个基于对话框的程序，它在建立对话框的时候调用前面的DLL，登记热键，因此需要将hook.lib添加到工程里，在程序里给出两个DLL函数的定义，也可以写个头文件，再包含进来以下代码：
BOOL __declspec(dllexport)__stdcall AddHotkey(HWND,UCHAR key,UCHAR mask);
BOOL __declspec(dllexport)__stdcall DeleteHotkey(HWND,UCHAR key,UCHAR mask);
为了添加应用程序对热键通知事件的响应，程序中用的办法是重载WindowProc（）函数，该函数代码如下：
LRESULT CCaptureDlg::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
if(message==WM_HOTKEY&&lParam==WM_KEYDOWN)
{ //lParam表示是按下还是松开，如果有多个热键，由wParam来区分
SaveBmp();
return FALSE;
}
…… //其它处理及默认处理
}
将屏幕图像保存到BMP文件中的任务是由函数SaveBmp（）来完成的，具体实现参见代码部分。另外为了顺利实现屏幕抓图，程序中还实现了"托盘"功能，由于这一部分本书在实例中已经专门介绍过了，所以不再赘述，读者朋友可以参考相关实例。
最后需要提醒读者朋友们注意的是，源程序的编译与使用时要先编译hook.dll并将其放在系统目录（win2000/NT是system32，98/ME是system），然后编译对话框程序运行即可。
二、编程步骤
1、 启动Visual C++，生成一个DLL项目和一个基于对话框的应用程序项目，并将两个项目分别命名为"Hook"和"Capture"；
2、 在"Hook"项目中导出AddHotkey（）、DeleteHotkey（）函数；
3、 在"Capture"项目中按照图一所示设置对话框的界面，具体设置参见代码部分；
4、 使用Class Wizard在"Capture"项目中添加按钮的鼠标单击消息响应函数，并重载对话框的WindowProc（）函数；
5、 添加代码，编译运行程序。
三、程序代码
/////////////////////////////////////////////////////////// Hook.h : main header file for the HOOK DLL
#if !defined(AFX_HOOK_H__AEBFF705_C93A_11D5_B7D6_0080C82BE86B__INCLUDED_)
#define AFX_HOOK_H__AEBFF705_C93A_11D5_B7D6_0080C82BE86B__INCLUDED_
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000
#ifndef __AFXWIN_H__
#error include ''stdafx.h'' before including this file for PCH
#endif
#include "resource.h" // main symbols
class CHookApp : public CWinApp
{
public:
CHookApp();
// Overrides
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CHookApp)
public:
virtual BOOL InitInstance();
virtual int ExitInstance();
//}}AFX_VIRTUAL
//{{AFX_MSG(CHookApp)
// NOTE - the ClassWizard will add and remove member functions here.
// DO NOT EDIT what you see in these blocks of generated code !
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
LRESULT CALLBACK KeyboardProc(int nCode,WPARAM wParam, LPARAM lParam);
BOOL __declspec(dllexport)__stdcall AddHotkey(HWND,UCHAR key,UCHAR mask);
BOOL __declspec(dllexport)__stdcall DeleteHotkey(HWND,UCHAR key,UCHAR mask);
BOOL InitHotkey();
BOOL UnInit();
#endif
////////// Hook.cpp : Defines the initialization routines for the DLL.
#include "stdafx.h"
#include "hook.h"
#include <windowsx.h>
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
#define MAX_KEY 100
#define CTRLBIT 0x04
#define ALTBIT 0x02
#define SHIFTBIT 0x01
#pragma data_seg("shareddata")
HHOOK hHook =NULL;
UINT nHookCount =0;
static UCHAR HotKey[MAX_KEY] = {0}; //hotkey
static UCHAR HotKeyMask[MAX_KEY] = {0}; //flag for hotkey, value is VK_CONTRL or VK_NEMU or VK_SHIFT
static HWND hCallWnd[MAX_KEY] = {0}; //window associated with hotkey
static int KeyCount =0;
static UCHAR MaskBits =0; //00000 Ctrl Alt Shift
#pragma data_seg()
HINSTANCE hins;
void VerifyWindow();
BEGIN_MESSAGE_MAP(CHookApp, CWinApp)
//{{AFX_MSG_MAP(CHookApp)
// NOTE - the ClassWizard will add and remove mapping macros here.
// DO NOT EDIT what you see in these blocks of generated code!
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
CHookApp::CHookApp()
{
// TODO: add construction code here,
// Place all significant initialization in InitInstance
}
CHookApp theApp;
LRESULT CALLBACK KeyboardProc(int nCode,WPARAM wParam,LPARAM lParam)
{
BOOL bProcessed=FALSE;
if(HC_ACTION==nCode)
{
if((lParam&0xc0000000)==0xc0000000){// Key up
switch(wParam)
{
case VK_MENU:
MaskBits&=~ALTBIT;
break;
case VK_CONTROL:
MaskBits&=~CTRLBIT;
break;
case VK_SHIFT:
MaskBits&=~SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYUP);
bProcessed=TRUE;
}
}
}
else if((lParam&0xc000ffff)==1){ //Key down
switch(wParam)
{
case VK_MENU:
MaskBits|=ALTBIT;
break;
case VK_CONTROL:
MaskBits|=CTRLBIT;
break;
case VK_SHIFT:
MaskBits|=SHIFTBIT;
break;
default: //judge the key and send message
break;
}
for(int index=0;index<MAX_KEY;index++)
{
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==wParam)&&(HotKeyMask[index]==MaskBits))
{
SendMessage(hCallWnd[index],WM_HOTKEY,wParam,WM_KEYDOWN);
bProcessed=TRUE;
}
}
}
if(!bProcessed){
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==NULL)
continue;
if(IsWindow(hCallWnd[index])&&(HotKey[index]==0)&&(HotKeyMask[index]==0))
SendMessage(hCallWnd[index],WM_HOTKEY,WM_HOTKEY,lParam);
}
}
}
return CallNextHookEx( hHook, nCode, wParam, lParam );
}
BOOL InitHotkey()
{
if(hHook!=NULL){
nHookCount++;
return TRUE;
}
else
hHook=SetWindowsHookEx(WH_KEYBOARD,(HOOKPROC)KeyboardProc,hins,0);
if(hHook!=NULL)
nHookCount++;
return (hHook!=NULL);
}
BOOL UnInit()
{
if(nHookCount>1){
nHookCount--;
return TRUE;
}
BOOL unhooked = UnhookWindowsHookEx(hHook);
if(unhooked==TRUE){
nHookCount=0;
hHook=NULL;
}
return unhooked;
}
BOOL __declspec(dllexport) __stdcall AddHotkey(HWND hWnd,UCHAR cKey,UCHAR cMask)
{
BOOL bAdded=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==0){
hCallWnd[index]=hWnd;
HotKey[index]=cKey;
HotKeyMask[index]=cMask;
bAdded=TRUE;
KeyCount++;
break;
}
}
return bAdded;
}
BOOL __declspec(dllexport) __stdcall DeleteHotkey(HWND hWnd,UCHAR cKey,UCHAR cMask)
{
BOOL bRemoved=FALSE;
for(int index=0;index<MAX_KEY;index++){
if(hCallWnd[index]==hWnd){
if(HotKey[index]==cKey&&HotKeyMask[index]==cMask){
hCallWnd[index]=NULL;
HotKey[index]=0;
HotKeyMask[index]=0;
bRemoved=TRUE;
KeyCount--;
break;
}
}
}
return bRemoved;
}
void VerifyWindow()
{
for(int i=0;i<MAX_KEY;i++){
if(hCallWnd[i]!=NULL){
if(!IsWindow(hCallWnd[i])){
hCallWnd[i]=NULL;
HotKey[i]=0;
HotKeyMask[i]=0;
KeyCount--;
}
}
}
}
BOOL CHookApp::InitInstance()
{
AFX_MANAGE_STATE(AfxGetStaticModuleState());
hins=AfxGetInstanceHandle();
InitHotkey();
return CWinApp::InitInstance();
}
int CHookApp::ExitInstance()
{
VerifyWindow();
UnInit();
return CWinApp::ExitInstance();
}
////////////////////////////////////////////////////////////////////// CaptureDlg.h : header file
#if !defined(AFX_CAPTUREDLG_H__97B51708_C928_11D5_B7D6_0080C82BE86B__INCLUDED_)
#define AFX_CAPTUREDLG_H__97B51708_C928_11D5_B7D6_0080C82BE86B__INCLUDED_
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000
class CCaptureDlg : public CDialog
{
// Construction
public:
BOOL bTray;
BOOL bRegistered;
BOOL RegisterHotkey();
UCHAR cKey;
UCHAR cMask;
void DeleteIcon();
void AddIcon();
UINT nCount;
void SaveBmp();
CCaptureDlg(CWnd* pParent = NULL); // standard constructor
// Dialog Data
//{{AFX_DATA(CCaptureDlg)
enum { IDD = IDD_CAPTURE_DIALOG };
CComboBox m_Key;
BOOL m_bControl;
BOOL m_bAlt;
BOOL m_bShift;
CString m_Path;
CString m_Number;
//}}AFX_DATA
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CCaptureDlg)
public:
virtual BOOL PreTranslateMessage(MSG* pMsg);
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
virtual LRESULT WindowProc(UINT message, WPARAM wParam, LPARAM lParam);
//}}AFX_VIRTUAL
// Implementation
protected:
HICON m_hIcon;
// Generated message map functions
//{{AFX_MSG(CCaptureDlg)
virtual BOOL OnInitDialog();
afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
afx_msg void OnPaint();
afx_msg HCURSOR OnQueryDragIcon();
virtual void OnCancel();
afx_msg void OnAbout();
afx_msg void OnBrowse();
afx_msg void OnChange();
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
#endif
////////////////////// CaptureDlg.cpp : implementation file
#include "stdafx.h"
#include "Capture.h"
#include "CaptureDlg.h"
#include <windowsx.h>
#pragma comment(lib,"hook.lib")
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
#define IDM_SHELL WM_USER+1
BOOL __declspec(dllexport)__stdcall AddHotkey(HWND,UCHAR key,UCHAR mask);
BOOL __declspec(dllexport)__stdcall DeleteHotkey(HWND,UCHAR key,UCHAR mask);
UCHAR Key_Table[]={0x78,0x79,0x7a,0x7b,0x6a,0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39};
class CAboutDlg : public CDialog
{
public:
CAboutDlg();
// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL
// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}
void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
CCaptureDlg::CCaptureDlg(CWnd* pParent /*=NULL*/)
: CDialog(CCaptureDlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CCaptureDlg)
m_bControl = FALSE;
m_bAlt = FALSE;
m_bShift = FALSE;
m_Path = _T("c:");
m_Number = _T("0 picture captured.");
nCount=0;
bRegistered=FALSE;
bTray=FALSE;
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}
void CCaptureDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CCaptureDlg)
DDX_Control(pDX, IDC_KEY, m_Key);
DDX_Check(pDX, IDC_CONTROL, m_bControl);
DDX_Check(pDX, IDC_ALT, m_bAlt);
DDX_Check(pDX, IDC_SHIFT, m_bShift);
DDX_Text(pDX, IDC_PATH, m_Path);
DDX_Text(pDX, IDC_NUMBER, m_Number);
//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CCaptureDlg, CDialog)
//{{AFX_MSG_MAP(CCaptureDlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_BN_CLICKED(ID_ABOUT, OnAbout)
ON_BN_CLICKED(IDC_BROWSE, OnBrowse)
ON_BN_CLICKED(ID_CHANGE, OnChange)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
BOOL CCaptureDlg::OnInitDialog()
{
CDialog::OnInitDialog();
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000);
CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
}
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon
m_Key.SetCurSel(0);
RegisterHotkey();
CMenu* pMenu=GetSystemMenu(FALSE);
pMenu->DeleteMenu(SC_MAXIMIZE,MF_BYCOMMAND);
pMenu->DeleteMenu(SC_SIZE,MF_BYCOMMAND);
pMenu->DeleteMenu(SC_RESTORE,MF_BYCOMMAND);
return TRUE; // return TRUE unless you set the focus to a control
}
void CCaptureDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}
void CCaptureDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting
SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);
// Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;
// Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}
HCURSOR CCaptureDlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}
void CCaptureDlg::OnCancel()
{
if(bTray)
DeleteIcon();
CDialog::OnCancel();
}
void CCaptureDlg::OnAbout()
{
CAboutDlg dlg;
dlg.DoModal();
}
void CCaptureDlg::OnBrowse()
{
CString str;
BROWSEINFO bi;
char name[MAX_PATH];
ZeroMemory(&bi,sizeof(BROWSEINFO));
bi.hwndOwner=GetSafeHwnd();
bi.pszDisplayName=name;
bi.lpszTitle="Select folder";
bi.ulFlags=BIF_RETURNONLYFSDIRS;
LPITEMIDLIST idl=SHBrowseForFolder(&bi);
if(idl==NULL)
return;
SHGetPathFromIDList(idl,str.GetBuffer(MAX_PATH));
str.ReleaseBuffer();
m_Path=str;
if(str.GetAt(str.GetLength()-1)!='''')
m_Path+="";
UpdateData(FALSE);
}
void CCaptureDlg::SaveBmp()
{
CDC dc;
dc.CreateDC("DISPLAY",NULL,NULL,NULL);
CBitmap bm;
int Width=GetSystemMetrics(SM_CXSCREEN);
int Height=GetSystemMetrics(SM_CYSCREEN);
bm.CreateCompatibleBitmap(&dc,Width,Height);
CDC tdc;
tdc.CreateCompatibleDC(&dc);
CBitmap*pOld=tdc.SelectObject(&bm);
tdc.BitBlt(0,0,Width,Height,&dc,0,0,SRCCOPY);
tdc.SelectObject(pOld);
BITMAP btm;
bm.GetBitmap(&btm);
DWORD size=btm.bmWidthBytes*btm.bmHeight;
LPSTR lpData=(LPSTR)GlobalAllocPtr(GPTR,size);
BITMAPINFOHEADER bih;
bih.biBitCount=btm.bmBitsPixel;
bih.biClrImportant=0;
bih.biClrUsed=0;
bih.biCompression=0;
bih.biHeight=btm.bmHeight;
bih.biPlanes=1;
bih.biSize=sizeof(BITMAPINFOHEADER);
bih.biSizeImage=size;
bih.biWidth=btm.bmWidth;
bih.biXPelsPerMeter=0;
bih.biYPelsPerMeter=0;
GetDIBits(dc,bm,0,bih.biHeight,lpData,(BITMAPINFO*)&bih,DIB_RGB_COLORS);
static int filecount=0;
CString name;
name.Format("pict%04d.bmp",filecount++);
name=m_Path+name;
BITMAPFILEHEADER bfh;
bfh.bfReserved1=bfh.bfReserved2=0;
bfh.bfType=((WORD)(''M''<< 8)|''B'');
bfh.bfSize=54+size;
bfh.bfOffBits=54;
CFile bf;
if(bf.Open(name,CFile::modeCreate|CFile::modeWrite)){
bf.WriteHuge(&bfh,sizeof(BITMAPFILEHEADER));
bf.WriteHuge(&bih,sizeof(BITMAPINFOHEADER));
bf.WriteHuge(lpData,size);
bf.Close();
nCount++;
}
GlobalFreePtr(lpData);
if(nCount==1)
m_Number.Format("%d picture captured.",nCount);
else
m_Number.Format("%d pictures captured.",nCount);
UpdateData(FALSE);
}
BOOL CCaptureDlg::PreTranslateMessage(MSG* pMsg)
{
if(pMsg -> message == WM_KEYDOWN)
{
if(pMsg -> wParam == VK_ESCAPE)
return TRUE;
if(pMsg -> wParam == VK_RETURN)
return TRUE;
}
return CDialog::PreTranslateMessage(pMsg);
}
LRESULT CCaptureDlg::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
if(message==WM_HOTKEY&&lParam==WM_KEYDOWN){
SaveBmp();
return FALSE;
}
if(message==IDM_SHELL&&lParam==WM_RBUTTONUP){
CMenu pop;
pop.LoadMenu(MAKEINTRESOURCE(IDR_MENU1));
CMenu*pMenu=pop.GetSubMenu(0);
pMenu->SetDefaultItem(ID_EXITICON);
CPoint pt;
GetCursorPos(&pt);
int id=pMenu->TrackPopupMenu(TPM_RIGHTALIGN|TPM_NONOTIFY|TPM_RETURNCMD|TPM_LEFTBUTTON,pt.x,pt.y,this);
if(id==ID_EXITICON)
DeleteIcon();
else if(id==ID_EXIT)
OnCancel();
return FALSE;
}
LRESULT res= CDialog::WindowProc(message, wParam, lParam);
if(message==WM_SYSCOMMAND&&wParam==SC_MINIMIZE)
AddIcon();
return res;
}
void CCaptureDlg::AddIcon()
{
NOTIFYICONDATA data;
data.cbSize=sizeof(NOTIFYICONDATA);
CString tip;
tip.LoadString(IDS_ICONTIP);
data.hIcon=GetIcon(0);
data.hWnd=GetSafeHwnd();
strcpy(data.szTip,tip);
data.uCallbackMessage=IDM_SHELL;
data.uFlags=NIF_ICON|NIF_MESSAGE |NIF_TIP ;
data.uID=98;
Shell_NotifyIcon(NIM_ADD,&data);
ShowWindow(SW_HIDE);
bTray=TRUE;
}
void CCaptureDlg::DeleteIcon()
{
NOTIFYICONDATA data;
data.cbSize=sizeof(NOTIFYICONDATA);
data.hWnd=GetSafeHwnd();
data.uID=98;
Shell_NotifyIcon(NIM_DELETE,&data);
ShowWindow(SW_SHOW);
SetForegroundWindow();
ShowWindow(SW_SHOWNORMAL);
bTray=FALSE;
}
void CCaptureDlg::OnChange()
{
RegisterHotkey();
}
BOOL CCaptureDlg::RegisterHotkey()
{
UpdateData();
UCHAR mask=0;
UCHAR key=0;
if(m_bControl)
mask|=4;
if(m_bAlt)
mask|=2;
if(m_bShift)
mask|=1;
key=Key_Table[m_Key.GetCurSel()];
if(bRegistered){
DeleteHotkey(GetSafeHwnd(),cKey,cMask);
bRegistered=FALSE;
}
cMask=mask;
cKey=key;
bRegistered=AddHotkey(GetSafeHwnd(),cKey,cMask);
return bRegistered;
}
四、小结
本实例通过一个钩子DLL实现了屏幕抓图的功能，它有一个缺陷，那就是只能保存整个屏幕图像，不过读者朋友可以在此基础上，实现屏幕任意区域的抓图功能，具体方法不再赘述，实现起来很容易的了，呵呵。
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