求大神指教这个程序错在哪

Question

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//#include "stdafx.h"

#include

#include

#include

//#pragma comment(/Entry:WinMain)

#define ID_TIMER 1

#define SNOWNUM 500 // 雪花数量

#define CONTRAST 50 // 对比度

#define YSTART 5 // 用于确定雪花初始时的y坐标

#define SNOWCR RGB(0xFF, 0xFF, 0xFF) //雪花的颜色—白色

#define SNOWGATHERCR RGB(0xDB, 0xDB, 0xFF) //堆积雪花的颜色

typedef struct tagSnow

{

POINT ptSnowsPos[SNOWNUM]; //用于保存各个雪花的坐标

COLORREF crOrg[SNOWNUM]; //用于画雪花前屏幕原来的颜色

int iVx, iVy, iAllVx, iAllVy;

}Snow;

void initSnow(HDC hdc, Snow *sn, int iSnow, int cxScreen);

int GetContrast(HDC hdc, Snow *sn, int iSnow);

void drawSnow(HDC hdc, Snow *sn, int cxScreen);

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,

PSTR szCmdLine, int iCmdShow)

{

static TCHAR szAppName[] = TEXT ("clsDeskSnow") ;

HWND hwnd ;

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;   
    }   

    hwnd = CreateWindow (szAppName,        TEXT ("桌面下雪"),   
                        WS_MINIMIZEBOX | WS_SYSMENU,   
                        CW_USEDEFAULT, CW_USEDEFAULT,   
                        240, 120,   
                        NULL, NULL, hInstance, NULL) ;   

    ShowWindow (hwnd, iCmdShow) ;   
    UpdateWindow (hwnd) ;   

    while (GetMessage (&msg, NULL, 0, 0))   
    {   
        TranslateMessage (&msg) ;   
        DispatchMessage (&msg) ;   
    }   
    return msg.wParam ;   

}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

{

HDC hdc ;

PAINTSTRUCT ps ;

RECT rect ;

static int cxScreen, cyScreen; //屏幕宽高度(单位:像素)

static int iTimes, iLoopTimes=100;

static Snow snowDream;

int i;

  switch (message)   
  {   
    case WM_CREATE:   
        cxScreen = GetSystemMetrics (SM_CXSCREEN) ;   
        cyScreen = GetSystemMetrics (SM_CYSCREEN) ;   
        srand ((int) GetCurrentTime ()) ; //初始化随机数发生器    
        snowDream.iAllVx = (unsigned)rand()%3 - 1; //雪花总体水平飘行速度(-1,0,1)    
        snowDream.iAllVy = (unsigned)rand()%2 + 1; //雪花总体垂直下落速度(1,2)    
        hdc = GetDC(NULL); //检索整个屏幕的设备上下文环境    
        for(i=0; i <SNOWNUM; i++)   
        {   
            snowDream.ptSnowsPos[i].x = rand() % cxScreen; //一个雪花开始下落的x坐标    
            snowDream.ptSnowsPos[i].y = rand() % YSTART; //一个雪花开始下落的y坐标    
            snowDream.crOrg[i] = GetPixel(hdc, snowDream.ptSnowsPos[i].x,   
                      snowDream.ptSnowsPos[i].y); //获取给定点的原来的颜色值    
        }   
        ReleaseDC(NULL, hdc);   
        SetTimer(hwnd, ID_TIMER, 10, NULL); //定时器，10毫秒    
        return 0 ;   

    case WM_DISPLAYCHANGE: //当显示分辨率改变的时候    
        cxScreen = GetSystemMetrics (SM_CXSCREEN) ;   
        cyScreen = GetSystemMetrics (SM_CYSCREEN) ;   
        return 0;   

    case WM_TIMER:   
        hdc = GetDC(NULL); //检索整个屏幕的设备上下文环境    
        if(iTimes > iLoopTimes)   
        {   
            iTimes = 0;   
            iLoopTimes = 50 + (unsigned)rand()%50;   
            if(snowDream.iAllVx != 0)   
              snowDream.iAllVx = 0;   
            else                    
              snowDream.iAllVx = (unsigned)rand()%3 - 1; //雪花总体水平飘行速度(-1,0,1)    
            snowDream.iAllVy = (unsigned)rand()%2 + 1; //雪花总体垂直下落速度(1,2)    
        }   
        else   
            iTimes++;   
        drawSnow(hdc, &snowDream, cxScreen);   
        ReleaseDC(NULL, hdc);   
        return 0;   

    case WM_PAINT:   
        hdc = BeginPaint (hwnd, &ps) ;   
        GetClientRect (hwnd, &rect) ;   
        DrawText (hdc, TEXT ("桌面下雪!"), -1, &rect,   
                  DT_SINGLELINE | DT_CENTER | DT_VCENTER) ;   
        EndPaint (hwnd, &ps) ;   
        return 0 ;   

    case WM_DESTROY:   
        KillTimer(hwnd, ID_TIMER); // 中止定时器    
        InvalidateRect(NULL, NULL, TRUE); // 刷新桌面    
        PostQuitMessage (0) ;   
        return 0 ;   
    }   
    return DefWindowProc (hwnd, message, wParam, lParam) ;   

}

void initSnow(HDC hdc, Snow *sn, int iSnow, int cxScreen) //初始化第iSnow个雪花

{

sn->ptSnowsPos[iSnow].x = (unsigned)rand() % cxScreen; //x范围整个屏幕宽

sn->ptSnowsPos[iSnow].y = (unsigned)rand() % YSTART; //y范围离屏幕顶部YSTART像素点以内

sn->crOrg[iSnow] = GetPixel(hdc, sn->ptSnowsPos[iSnow].x,

sn->ptSnowsPos[iSnow].y ) ;//获取给定点的原来的颜色值

}

int GetContrast(HDC hdc, Snow *sn, int iSnow)

{

int iR, iG, iB;

COLORREF crCmp;

if(0 == sn->iVx) //若水平速度为0，则取比其大一个像素的正下方的点

crCmp = GetPixel(hdc, sn->ptSnowsPos[iSnow].x, sn->ptSnowsPos[iSnow].y + 1);

else //若水平速度>0，取右下方的点。 crCmp = GetPixel(hdc, sn->ptSnowsPos[iSnow].x + (sn->iVx>0?1:-1), sn->ptSnowsPos[iSnow].y + 1);

if(crCmp==SNOWCR) //如果为雪花的颜色

return 0;

//分别获取crCmp与对比点的蓝、绿、红部分的差值

iB = abs((crCmp>>16)&0xFF - (sn->crOrg[iSnow]>>16)&0xFF);

iG = abs((crCmp>>8)&0xFF - (sn->crOrg[iSnow]>>8)&0xFF);

iR = abs((crCmp)&0xFF - (sn->crOrg[iSnow])&0xFF);

return (iR+iG+iB)/3;

}

void drawSnow(HDC hdc, Snow *sn, int cxScreen)

{

int i;

for(i=0; i {
//如果保存的原来的颜色不是雪花的颜色
if(sn->crOrg[i] != SNOWCR)

SetPixel(hdc, sn->ptSnowsPos[i].x, sn->ptSnowsPos[i].y,

sn->crOrg[i]); //还原上一个位置的颜色

  sn->iVx = sn->iAllVx*(i%3+1); //雪花的x飘动速度    
  sn->iVy = sn->iAllVy*(i%3+1); //雪花的y飘动速度    
  //rand()%5-2使雪花下落的时候 有抖动效果    
  sn->ptSnowsPos[i].x += sn->iVx+rand()%5-2; //雪花的下一个x坐标    
  sn->ptSnowsPos[i].y += sn->iVy+1; //雪花的下一个y坐标    

  //获取给定点的原来的颜色值    
  sn->crOrg[i] = GetPixel(hdc, sn->ptSnowsPos[i].x, sn->ptSnowsPos[i].y);   

  if(CLR_INVALID == sn->crOrg[i]) //如果获取颜色失败,即雪花飘出了屏幕    
  {   
    initSnow(hdc, sn, i, cxScreen); //重新初始化 雪花    
    continue;   
  }   
  if(sn->crOrg[i] != SNOWCR) //若当前点的颜色 不等于 雪花的颜色    
  {   
    if(SNOWGATHERCR == sn->crOrg[i]) //当前点的颜色=堆积的雪的颜色    
  {  //设置为雪花的颜色    
      SetPixel(hdc, sn->ptSnowsPos[i].x, sn->ptSnowsPos[i].y, SNOWCR);   
      sn->crOrg[i] = SNOWCR;   
      //initSnow(hdc, sn, i, cxScreen); //重新初始化 雪花    
  }   
  else if(GetContrast(hdc, sn, i) > 50) //若对比度>50    
    {  //堆积雪花    
        SetPixel(hdc, sn->ptSnowsPos[i].x,  sn->ptSnowsPos[i].y,  SNOWGATHERCR);   
        SetPixel(hdc, sn->ptSnowsPos[i].x-1, sn->ptSnowsPos[i].y+1, SNOWGATHERCR);   
        SetPixel(hdc, sn->ptSnowsPos[i].x+1, sn->ptSnowsPos[i].y+1, SNOWGATHERCR);   
        initSnow(hdc, sn, i, cxScreen); //重新初始化 雪花    
    }   
    else //对比度 <50,不堆积,画出这帧雪花.等下次的时候再还原此点原本的颜色.以产生飘动效果    
      SetPixel(hdc, sn->ptSnowsPos[i].x, sn->ptSnowsPos[i].y, SNOWCR);   
  }   

}

}