我正在尝试找出如何使 Windows 桌面淡出或变暗，然后正常显示桌面的矩形部分。这是一个屏幕区域捕获程序。你可以在 Jing 中看到我想要的精确效果淡化网页中的背景也很常见。非常感谢任何提示/指针/C++ 源代码。谷歌到目前为止没有帮助。

谢谢， 内维尔

最佳答案

使用覆盖整个屏幕的分层窗口，但使用颜色键值对其进行绘制，以便感兴趣的矩形区域(应该不暗的区域)完全被颜色键填充。该区域将完全透明，不会像桌面的其他部分那样变暗。分层窗口的其余部分应设置为具有恒定的 alpha 值，该值大部分是透明的并填充深色。

这是一个完整的工作示例:

#include "stdafx.h"
#include "ScreenCapper.h"

#define MAX_LOADSTRING 100

// Global Variables:
HINSTANCE hInst;                                // current instance
TCHAR szTitle[MAX_LOADSTRING];                  // The title bar text
TCHAR 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);

const COLORREF transparentColor = RGB(255,0,0); // Pure red is the color key, or totally transparent color
const BYTE overallTranparencyAmount = 90; // Out of 255
int DesktopWidth,DesktopHeight;

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

    DesktopWidth = GetSystemMetrics(SM_CXSCREEN);
    DesktopHeight = GetSystemMetrics(SM_CYSCREEN);

    MSG msg;
    HACCEL hAccelTable;

    LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
    LoadString(hInstance, IDC_SCREENCAPPER, szWindowClass, MAX_LOADSTRING);
    MyRegisterClass(hInstance);

    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }

    hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_SCREENCAPPER));

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

    return (int) msg.wParam;
}

ATOM MyRegisterClass(HINSTANCE hInstance)
{
    WNDCLASSEX wcex;

    memset(&wcex,0,sizeof(WNDCLASSEX));
    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_SCREENCAPPER));
    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
    //wcex.lpszMenuName = MAKEINTRESOURCE(IDC_SCREENCAPPER);
    wcex.lpszClassName  = szWindowClass;
    wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

    return RegisterClassEx(&wcex);
}

BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
    hInst = hInstance;
    HWND hWnd = CreateWindowEx(WS_EX_LAYERED, szWindowClass, szTitle,WS_POPUP, 0, 0, DesktopWidth, DesktopHeight, NULL, NULL, hInstance, NULL);
    if (!hWnd)
        return FALSE;
    SetLayeredWindowAttributes(hWnd,transparentColor,32,LWA_COLORKEY | LWA_ALPHA);

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

    return TRUE;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int wmId, wmEvent;
    PAINTSTRUCT ps;
    HDC hdc;

    if (message == WM_COMMAND)
    {
        wmId    = LOWORD(wParam);
        wmEvent = HIWORD(wParam);
        // Parse the menu selections:
        switch (wmId)
        {
            case IDM_EXIT:
                DestroyWindow(hWnd);
                break;
            default:
                return DefWindowProc(hWnd, message, wParam, lParam);
        }
    }
    else if (message == WM_PAINT)
    {
        hdc = BeginPaint(hWnd, &ps);

        HBRUSH hDarkBackgroundBrush = CreateSolidBrush(RGB(0,0,0));
        HBRUSH hRegionOfInterestBrush = CreateSolidBrush(transparentColor);

        RECT screenRect;
        screenRect.left = screenRect.top = 0;
        screenRect.right = DesktopWidth;
        screenRect.bottom = DesktopHeight;

        RECT interestRect;
        interestRect.left = interestRect.top = 300;
        interestRect.right = interestRect.bottom = 600;
        FillRect(hdc,&screenRect,hDarkBackgroundBrush);
        FillRect(hdc,&interestRect,hRegionOfInterestBrush);

        DeleteObject(hDarkBackgroundBrush);
        DeleteObject(hRegionOfInterestBrush);
        EndPaint(hWnd, &ps);
    }
    else if (message == WM_DESTROY)
    {
        PostQuitMessage(0);
    }
    else
        return DefWindowProc(hWnd, message, wParam, lParam);
    return 0;
}

关于c++ - 在 C++ 中淡化 Windows 桌面，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/1591131/