编写的屏幕下雪小程序，有一个错误，望朋友们指教一下如何改正！（大家可实现一下，改正后效果很好玩）
#include <windows.h>#include <math.h>
#include <stdlib.h>
#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();
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。 <0则取左下方的点
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 <SNOWNUM; 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);
}
}
}
[ 本帖最后由 阿彬 于 2013-10-30 11:17 编辑 ]
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