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我想要通过窗口句柄获取一个窗口的截图,这个窗口是一个外部程序的,只知道进程号,然后回显到当前正在运行的程序窗口上。
这些代码是我从https://learn.microsoft.com/en-us/windows/win32/gdi/capturing-an-image复制下来的,在147行GetDC(NULL)获取桌面窗口句柄,这样可以成功显示。
但是当我把GetDC()参数换成上面这种通过进程ID获取的窗口句柄时,显示都是黑屏的。我不知道是什么原因,求大佬解答 - BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam)
- {
- EnumWindowsArg* pArg = (EnumWindowsArg*)lParam;
- DWORD dwProcessID = 0;
- // 通过窗口句柄取得进程ID
- ::GetWindowThreadProcessId(hwnd, &dwProcessID);
- if (dwProcessID == pArg->dwProcessID)
- {
- pArg->hwndWindow = hwnd;
- // 找到了返回FALSE
- return FALSE;
- }
- // 没找到,继续找,返回TRUE
- return TRUE;
- }
- ///< 通过进程ID获取窗口句柄
- HWND GetWindowHwndByPID(DWORD dwProcessID)
- {
- HWND hwndRet = NULL;
- EnumWindowsArg ewa;
- ewa.dwProcessID = dwProcessID;
- ewa.hwndWindow = NULL;
- EnumWindows(EnumWindowsProc, (LPARAM)&ewa);
- if (ewa.hwndWindow)
- {
- hwndRet = ewa.hwndWindow;
- }
- return hwndRet;
- }
复制代码
- // GDI_CapturingAnImage.cpp : Defines the entry point for the application.
- //
- #include "framework.h"
- #include "GDI_CapturingAnImage.h"
- #include "GetHWND.h"
- #define MAX_LOADSTRING 100
- // Global Variables:
- HINSTANCE hInst; // current instance
- WCHAR szTitle[MAX_LOADSTRING]; // The title bar text
- WCHAR szWindowClass[MAX_LOADSTRING]; // 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_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM);
- int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
- _In_opt_ HINSTANCE hPrevInstance,
- _In_ LPWSTR lpCmdLine,
- _In_ int nCmdShow)
- {
- UNREFERENCED_PARAMETER(hPrevInstance);
- UNREFERENCED_PARAMETER(lpCmdLine);
- // TODO: Place code here.
- // Initialize global strings
- LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
- LoadStringW(hInstance, IDC_GDICAPTURINGANIMAGE, szWindowClass, MAX_LOADSTRING);
- MyRegisterClass(hInstance);
- // Perform application initialization:
- if (!InitInstance(hInstance, nCmdShow))
- {
- return FALSE;
- }
- HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_GDICAPTURINGANIMAGE));
- MSG msg;
- // Main message loop:
- while (GetMessage(&msg, nullptr, 0, 0))
- {
- if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
- {
- TranslateMessage(&msg);
- DispatchMessage(&msg);
- }
- }
- return (int)msg.wParam;
- }
- //
- // FUNCTION: MyRegisterClass()
- //
- // PURPOSE: Registers the window class.
- //
- ATOM MyRegisterClass(HINSTANCE hInstance)
- {
- WNDCLASSEXW 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 = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_GDICAPTURINGANIMAGE));
- wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
- wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
- wcex.lpszMenuName = MAKEINTRESOURCEW(IDC_GDICAPTURINGANIMAGE);
- wcex.lpszClassName = szWindowClass;
- wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
- return RegisterClassExW(&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)
- {
- hInst = hInstance; // Store instance handle in our global variable
- HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
- CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);
- 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 function attempts to create a file called captureqwsx.bmp
- //
- int CaptureAnImage(HWND hWnd)
- {
- HDC hdcScreen;
- HDC hdcWindow;
- HDC hdcMemDC = NULL;
- HBITMAP hbmScreen = NULL;
- BITMAP bmpScreen;
- DWORD dwBytesWritten = 0;
- DWORD dwSizeofDIB = 0;
- HANDLE hFile = NULL;
- char* lpbitmap = NULL;
- HANDLE hDIB = NULL;
- DWORD dwBmpSize = 0;
- // Retrieve the handle to a display device context for the client
- // area of the window.
- // HWND nhdcScreen = GetWindowHwndByPID(27380);
- hdcScreen = GetDC(NULL); // source
- hdcWindow = GetDC(hWnd); // destination
- // 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;
- 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.
- hDIB = GlobalAlloc(GHND, dwBmpSize);
- lpbitmap = (char*)GlobalLock(hDIB);
- // Gets the "bits" from the bitmap, and copies them into a buffer
- // that's 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.
- 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.
- 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.
- 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)
- {
- switch (message)
- {
- case WM_COMMAND:
- {
- int wmId = LOWORD(wParam);
- // Parse the menu selections:
- switch (wmId)
- {
- case IDM_ABOUT:
- DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
- break;
- case IDM_EXIT:
- DestroyWindow(hWnd);
- break;
- default:
- return DefWindowProc(hWnd, message, wParam, lParam);
- }
- }
- break;
- case WM_PAINT:
- {
- PAINTSTRUCT ps;
- HDC 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;
- }
- // Message handler for about box.
- INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
- {
- UNREFERENCED_PARAMETER(lParam);
- switch (message)
- {
- case WM_INITDIALOG:
- return (INT_PTR)TRUE;
- case WM_COMMAND:
- if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
- {
- EndDialog(hDlg, LOWORD(wParam));
- return (INT_PTR)TRUE;
- }
- break;
- }
- return (INT_PTR)FALSE;
- }
复制代码
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