屏幕截图

// GDI_CapturingAnImage.cpp : Defines the entry point for the application.
//

#include <tchar.h>
#include <Windows.h>

#define MAX_LOADSTRING 100

// Global Variables:
HINSTANCE hInst;                        // current instance
TCHAR szTitle[MAX_LOADSTRING] = L"CapturingAnImage";          // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING] = L"CapturingAnImage";    // the main window class name

// Forward declarations of functions included in this code module:
ATOM                MyRegisterClass(HINSTANCE hInstance);
BOOL                InitInstance(HINSTANCE, int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);

int APIENTRY _tWinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPTSTR    lpCmdLine,
int       nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);

MSG msg;
HACCEL hAccelTable;

MyRegisterClass(hInstance);

// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}

hAccelTable = NULL;

// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}

return (int) msg.wParam;
}

//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
//  COMMENTS:
//
//    This function and its usage are only necessary if you want this code
//    to be compatible with Win32 systems prior to the 'RegisterClassEx'
//    function that was added to Windows 95. It is important to call this function
//    so that the application will get 'well formed' small icons associated
//    with it.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEX wcex;

wcex.cbSize = sizeof(WNDCLASSEX);

wcex.style              = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc        = WndProc;
wcex.cbClsExtra         = 0;
wcex.cbWndExtra         = 0;
wcex.hInstance          = hInstance;
wcex.hIcon              = NULL;
wcex.hCursor            = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground      = (HBRUSH)(COLOR_WINDOW + 1);
wcex.lpszMenuName       = NULL;
wcex.lpszClassName      = szWindowClass;
wcex.hIconSm            = NULL;

return RegisterClassEx(&wcex);
}

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
HWND hWnd;

hInst = hInstance; // Store instance handle in our global variable

hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);

if (!hWnd)
{
return FALSE;
}

ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);

return TRUE;
}

// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
// PARTICULAR PURPOSE.
//
// Copyright (c) Microsoft Corporation. All rights reserved

//
//   FUNCTION: CaptureAnImage(HWND hWnd)
//
//   PURPOSE: Captures a screenshot into a window and then saves it in a .bmp file.
//
//   COMMENTS:
//
//      Note: This sample will attempt to create a file called captureqwsx.bmp
//

int CaptureAnImage(HWND hWnd)
{
HDC hdcScreen;
HDC hdcWindow;
HDC hdcMemDC = NULL;
HBITMAP hbmScreen = NULL;
BITMAP bmpScreen;

// Retrieve the handle to a display device context for the client
// area of the window.
hdcScreen = GetDC(NULL);
hdcWindow = GetDC(hWnd);

// Create a compatible DC which is used in a BitBlt from the window DC
hdcMemDC = CreateCompatibleDC(hdcWindow);

if(!hdcMemDC)
{
MessageBox(hWnd, L"CreateCompatibleDC has failed", L"Failed", MB_OK);
goto done;
}

// Get the client area for size calculation
RECT rcClient;
GetClientRect(hWnd, &rcClient);

//This is the best stretch mode
SetStretchBltMode(hdcWindow, HALFTONE);

//The source DC is the entire screen and the destination DC is the current window (HWND)
if(!StretchBlt(hdcWindow,
0,0,
rcClient.right, rcClient.bottom,
hdcScreen,
0,0,
GetSystemMetrics (SM_CXSCREEN),
GetSystemMetrics (SM_CYSCREEN),
SRCCOPY))
{
MessageBox(hWnd, L"StretchBlt has failed", L"Failed", MB_OK);
goto done;
}

// Create a compatible bitmap from the Window DC
hbmScreen = CreateCompatibleBitmap(hdcWindow, rcClient.right - rcClient.left, rcClient.bottom - rcClient.top);

if(!hbmScreen)
{
MessageBox(hWnd, L"CreateCompatibleBitmap Failed", L"Failed", MB_OK);
goto done;
}

// Select the compatible bitmap into the compatible memory DC.
SelectObject(hdcMemDC, hbmScreen);

// Bit block transfer into our compatible memory DC.
if(!BitBlt(hdcMemDC,
0,0,
rcClient.right - rcClient.left, rcClient.bottom - rcClient.top,
hdcWindow,
0,0,
SRCCOPY))
{
MessageBox(hWnd, L"BitBlt has failed", L"Failed", MB_OK);
goto done;
}

// Get the BITMAP from the HBITMAP
GetObject(hbmScreen, sizeof(BITMAP), &bmpScreen);

BITMAPFILEHEADER   bmfHeader;
BITMAPINFOHEADER   bi;

bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bmpScreen.bmWidth;
bi.biHeight = bmpScreen.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = 32;
bi.biCompression = BI_RGB;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

DWORD dwBmpSize = ((bmpScreen.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmpScreen.bmHeight;

// Starting with 32-bit Windows, GlobalAlloc and LocalAlloc are implemented as wrapper functions that
// call HeapAlloc using a handle to the process's default heap. Therefore, GlobalAlloc and LocalAlloc
// have greater overhead than HeapAlloc.
HANDLE hDIB = GlobalAlloc(GHND, dwBmpSize);
char *lpbitmap = (char *)GlobalLock(hDIB);

// Gets the "bits" from the bitmap and copies them into a buffer
// which is pointed to by lpbitmap.
GetDIBits(hdcWindow, hbmScreen, 0,
(UINT)bmpScreen.bmHeight,
lpbitmap,
(BITMAPINFO *)&bi, DIB_RGB_COLORS);

// A file is created, this is where we will save the screen capture.
HANDLE hFile = CreateFile(L"captureqwsx.bmp",
GENERIC_WRITE,
0,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL, NULL);

// Add the size of the headers to the size of the bitmap to get the total file size
DWORD dwSizeofDIB = dwBmpSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

//Offset to where the actual bitmap bits start.
bmfHeader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER);

//Size of the file
bmfHeader.bfSize = dwSizeofDIB;

//bfType must always be BM for Bitmaps
bmfHeader.bfType = 0x4D42; //BM

DWORD dwBytesWritten = 0;
WriteFile(hFile, (LPSTR)&bmfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)&bi, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)lpbitmap, dwBmpSize, &dwBytesWritten, NULL);

//Unlock and Free the DIB from the heap
GlobalUnlock(hDIB);
GlobalFree(hDIB);

//Close the handle for the file that was created
CloseHandle(hFile);

//Clean up
done:
DeleteObject(hbmScreen);
DeleteObject(hdcMemDC);
ReleaseDC(NULL, hdcScreen);
ReleaseDC(hWnd, hdcWindow);

return 0;
}

//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE:  Processes messages for the main window.
//
//  WM_COMMAND    - process the application menu
//  WM_PAINT    - Paint the main window
//  WM_DESTROY    - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;

switch (message)
{
case WM_CREATE:
{
break;
}
case WM_COMMAND:
wmId    = LOWORD(wParam);
wmEvent = HIWORD(wParam);

break;

case WM_MOVE:

case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
CaptureAnImage(hWnd);
EndPaint(hWnd, &ps);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}