纯win32实现PNG图片透明窗体

 

如果用g++编译需要加上libgdiplus.a,如果用msvc编译器需要加上gdiplus.lib 可以直接 #pragma comment(lib,"gdiplus.lib")

#include <windows.h>#include <gdiplus.h>/*  GDI+ startup token */ULONG_PTR gdiplusStartupToken;/*  Declare Windows procedure  */LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);// UpdateLayeredWindow Definationtypedef BOOL(*UPDATELAYEREDWINDOWFUNCTION)(HWND,HDC,POINT*,SIZE*,HDC,POINT*,COLORREF,BLENDFUNCTION*,DWORD);/*  Make the class name into a global variable  */char szClassName[ ] = "PNGDialog";int WINAPI WinMain (HINSTANCE hThisInstance,                     HINSTANCE hPrevInstance,                     LPSTR lpszArgument,                     int nCmdShow){    /**/    Gdiplus::GdiplusStartupInput gdiInput;    Gdiplus::GdiplusStartup(&gdiplusStartupToken,&gdiInput,NULL);    /**/    HWND hwnd;               /* This is the handle for our window */    MSG messages;            /* Here messages to the application are saved */    WNDCLASSEX wincl;        /* Data structure for the windowclass */    /* The Window structure */    wincl.hInstance = hThisInstance;    wincl.lpszClassName = szClassName;//+-69+    wincl.lpfnWndProc = WindowProcedure;      /* This function is called by windows */    wincl.style = CS_DBLCLKS;                 /* Catch double-clicks */    wincl.cbSize = sizeof (WNDCLASSEX);    /* Use default icon and mouse-pointer */    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);    wincl.lpszMenuName = NULL;                 /* No menu */    wincl.cbClsExtra = 0;                      /* No extra bytes after the window class */    wincl.cbWndExtra = 0;                      /* structure or the window instance */    /* Use Windows's default colour as the background of the window */    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;    /* Register the window class, and if it fails quit the program */    if (!RegisterClassEx (&wincl))        return 0;    /* The class is registered, let's create the program*/    hwnd = CreateWindowEx (           WS_EX_LAYERED|WS_EX_TOPMOST|WS_EX_TOOLWINDOW,                   /* Extended possibilites for variation */           szClassName,         /* Classname */           "PNGDialog Example Application",       /* Title Text */           WS_OVERLAPPEDWINDOW, /* default window */           CW_USEDEFAULT,       /* Windows decides the position */           CW_USEDEFAULT,       /* where the window ends up on the screen */           500,                 /* The programs width */           500,                 /* and height in pixels */           HWND_DESKTOP,        /* The window is a child-window to desktop */           NULL,                /* No menu */           hThisInstance,       /* Program Instance handler */           NULL                 /* No Window Creation data */           );    /* Make the window visible on the screen */    ShowWindow (hwnd, nCmdShow);    LONG style = ::GetWindowLong(hwnd,GWL_STYLE);    if(style&WS_CAPTION)        style^=WS_CAPTION;    if(style&WS_THICKFRAME)        style^=WS_THICKFRAME;    if(style&WS_SYSMENU)        style^=WS_SYSMENU;    ::SetWindowLong(hwnd,GWL_STYLE,style);    style = ::GetWindowLong(hwnd,GWL_EXSTYLE);    if(style&WS_EX_APPWINDOW)        style^=WS_EX_APPWINDOW;    ::SetWindowLong(hwnd,GWL_EXSTYLE,style);    /********************************************    *   step 1.    *   Using Gdiplus to load the image    ********************************************/    RECT wndRect;    ::GetWindowRect(hwnd,&wndRect);    SIZE wndSize = {wndRect.right-wndRect.left,wndRect.bottom-wndRect.top};    HDC hdc = ::GetDC(hwnd);    HDC memDC = ::CreateCompatibleDC(hdc);    HBITMAP memBitmap = ::CreateCompatibleBitmap(hdc,wndSize.cx,wndSize.cy);    ::SelectObject(memDC,memBitmap);    Gdiplus::Image image(L"pic.png");    Gdiplus::Graphics graphics(memDC);    graphics.DrawImage(&image,0,0,wndSize.cx,wndSize.cy);    /********************************************    *   step 2.    *   Get "UpdateLayeredWindow" function's    *   proc address.    ********************************************/    HMODULE hUser32 = ::LoadLibrary("User32.dll");    if(!hUser32)    {        return FALSE;    }    UPDATELAYEREDWINDOWFUNCTION UpdateLayeredWindow = (UPDATELAYEREDWINDOWFUNCTION)::GetProcAddress(hUser32,"UpdateLayeredWindow");    if(!UpdateLayeredWindow)    {        return FALSE;    }    // get screen dc    HDC screenDC = GetDC(NULL);    POINT ptSrc = {0,0};    /*********************************************    *   step 3.    *   Use UpdateLayeredWindow to Draw the Window    *    *********************************************/    BLENDFUNCTION blendFunction;    blendFunction.AlphaFormat = AC_SRC_ALPHA;    blendFunction.BlendFlags = 0;    blendFunction.BlendOp = AC_SRC_OVER;    blendFunction.SourceConstantAlpha = 255;    UpdateLayeredWindow(hwnd,screenDC,&ptSrc,&wndSize,memDC,&ptSrc,0,&blendFunction,2);    ::DeleteDC(memDC);    ::DeleteObject(memBitmap);    /* Run the message loop. It will run until GetMessage() returns 0 */    while (GetMessage (&messages, NULL, 0, 0))    {        /* Translate virtual-key messages into character messages */        TranslateMessage(&messages);        /* Send message to WindowProcedure */        DispatchMessage(&messages);    }    Gdiplus::GdiplusShutdown(gdiplusStartupToken);    /* The program return-value is 0 - The value that PostQuitMessage() gave */    return messages.wParam;}/*  This function is called by the Windows function DispatchMessage()  */LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam){    switch (message)                  /* handle the messages */    {        case WM_DESTROY:            PostQuitMessage (0);       /* send a WM_QUIT to the message queue */            break;        case WM_LBUTTONDOWN:            //::SendMessage(hwnd,WM_HIT)            break;        default:                      /* for messages that we don't deal with */            return DefWindowProc (hwnd, message, wParam, lParam);    }    return 0;}