8e 用定时器实现一个简单的取色器

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思路比较清晰获取当前鼠标位置的像素点的信息。。
/*------------------------------------------   WHATCLR.C -- Displays Color Under Cursor                (c) Charles Petzold, 1998  ------------------------------------------*/#include <windows.h>#define ID_TIMER    1void FindWindowSize (int *, int *) ;LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,                    PSTR szCmdLine, int iCmdShow){     static TCHAR szAppName[] = TEXT ("WhatClr") ;     HWND         hwnd ;     int          cxWindow, cyWindow ;     MSG          msg ;     WNDCLASS     wndclass ;          wndclass.style         = CS_HREDRAW | CS_VREDRAW ;     wndclass.lpfnWndProc   = WndProc ;     wndclass.cbClsExtra    = 0 ;     wndclass.cbWndExtra    = 0 ;     wndclass.hInstance     = hInstance ;     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;     wndclass.lpszMenuName  = NULL ;     wndclass.lpszClassName = szAppName ;          if (!RegisterClass (&wndclass))     {          MessageBox (NULL, TEXT ("This program requires Windows NT!"),                      szAppName, MB_ICONERROR) ;          return 0 ;     }          FindWindowSize (&cxWindow, &cyWindow) ;          hwnd = CreateWindow (szAppName, TEXT ("What Color"),                          WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_BORDER,                          CW_USEDEFAULT, CW_USEDEFAULT,                          cxWindow, cyWindow,                          NULL, NULL, hInstance, NULL) ;          ShowWindow (hwnd, iCmdShow) ;     UpdateWindow (hwnd) ;          while (GetMessage (&msg, NULL, 0, 0))     {          TranslateMessage (&msg) ;          DispatchMessage (&msg) ;     }     return msg.wParam ;}void FindWindowSize (int * pcxWindow, int * pcyWindow){     HDC        hdcScreen ;     TEXTMETRIC tm ;          hdcScreen = CreateIC (TEXT ("DISPLAY"), NULL, NULL, NULL) ;     GetTextMetrics (hdcScreen, &tm) ;     DeleteDC (hdcScreen) ;          * pcxWindow = 2 * GetSystemMetrics (SM_CXBORDER)  +                         12 * tm.tmAveCharWidth ;     * pcyWindow = 2 * GetSystemMetrics (SM_CYBORDER)  +                       GetSystemMetrics (SM_CYCAPTION) +                          2 * tm.tmHeight ;}LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam){     static COLORREF cr, crLast ;     static HDC      hdcScreen ;     HDC             hdc ;     PAINTSTRUCT     ps ;     POINT           pt ;     RECT            rc ;     TCHAR           szBuffer [16] ;          switch (message)     {     case WM_CREATE:          hdcScreen = CreateDC (TEXT ("DISPLAY"), NULL, NULL, NULL) ;          SetTimer (hwnd, ID_TIMER, 100, NULL) ;          return 0 ;     case WM_DISPLAYCHANGE:          DeleteDC (hdcScreen) ;          hdcScreen = CreateDC (TEXT ("DISPLAY"), NULL, NULL, NULL) ;          return 0 ;     case WM_TIMER:          GetCursorPos (&pt) ;          cr = GetPixel (hdcScreen, pt.x, pt.y) ;                    if (cr != crLast)          {               crLast = cr ;               InvalidateRect (hwnd, NULL, FALSE) ;          }          return 0 ;               case WM_PAINT:          hdc = BeginPaint (hwnd, &ps) ;                    GetClientRect (hwnd, &rc) ;                    wsprintf (szBuffer, TEXT ("  %02X %02X %02X  "),                    GetRValue (cr), GetGValue (cr), GetBValue (cr)) ;                    DrawText (hdc, szBuffer, -1, &rc,                    DT_SINGLELINE | DT_CENTER | DT_VCENTER) ;                    EndPaint (hwnd, &ps) ;          return 0 ;               case WM_DESTROY:          DeleteDC (hdcScreen) ;          KillTimer (hwnd, ID_TIMER) ;          PostQuitMessage (0) ;          return 0 ;     }     return DefWindowProc (hwnd, message, wParam, lParam) ;}
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