win32用GDI+加载png图片作为背景图

#include <windows.h>
#include <gdiplus.h>

/* GDI+ startup token */
ULONG_PTR gdiplusStartupToken;

/* Declare Windows procedure */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);

// UpdateLayeredWindow Defination
typedef 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;
}

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