更新时间:2015-12-16 00:56:56浏览次数:1+次
COLORREF clrClear = RGB(0,0,0);//合成创建一个黑色
for (int i=-2;i<=2;i++)
{
for (int j=-2;j<=2;j++)
{
SetPixel(hdc,GET_X_LPARAM(lParam)+i,GET_Y_LPARAM(lParam)+j,clrClear); //-单像素
}
}
GET_X_LPARAM(lParam)获取的是当前像素点的x坐标,GET_Y_LPARAM(lParam)获取的就是当前像素点的y坐标,然后分别-2和+2扩展后,双层循环就达到了形成一个像素块的效果。这里就是一个SetPixel函数来设置颜色。clrClear直接设置为了背景的黑色,用来擦除画的点。
可以从图中看到,已经被擦掉了一部分,C++技术网几个字已经不是完整的了,包括最顶上的一串。白色的字是图片水印。
以下是完整的源代码,你可以自己运行玩玩:
#include "windows.h"
#include <Windowsx.h>//GET_X_LPARAM,GET_Y_LPARAM宏需要这个头文件
#include <tchar.h>
// - 项目是Unicode字符集
LRESULT CALLBACK WinProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
static bool bisPaint=false;
static bool bisClear=false;
TCHAR Info[100]=_T("【C++技术网http://www.cjjjs.com】");
int iRed,iGreen,iBlue;
switch (message)
{
case WM_PAINT:
hdc = BeginPaint(hwnd,&ps);//会清除无效矩形
TextOut(hdc,0,10,Info,lstrlen(Info));
EndPaint(hwnd,&ps);
return 0;
case WM_LBUTTONDOWN:
bisPaint=true;//开始作画
return 0;
case WM_LBUTTONUP:
bisPaint=false;//松开鼠标,结束绘画
return 0;
case WM_RBUTTONDOWN:
bisClear=true;
return 0;
case WM_RBUTTONUP:
bisClear=false;
return 0;
case WM_MOUSEMOVE:
if(bisPaint)//如果按着鼠标时,表示在作画,因此可以开始绘制
{
hdc = GetDC(hwnd);
SetPixel(hdc,GET_X_LPARAM(lParam),GET_Y_LPARAM(lParam),RGB(200,0,0)); //-单像素
SetPixel(hdc,GET_X_LPARAM(lParam),GET_Y_LPARAM(lParam)+1,RGB(205,0,0)); //-单像素
SetPixel(hdc,GET_X_LPARAM(lParam)+1,GET_Y_LPARAM(lParam),RGB(5,0,0)); //-单像素
SetPixel(hdc,GET_X_LPARAM(lParam)+1,GET_Y_LPARAM(lParam)+1,RGB(55,0,0)); //-单像素
ReleaseDC(hwnd,hdc);
}
if(bisClear)
{
//-擦除绘图
hdc = GetDC(hwnd);
COLORREF clr = GetPixel(hdc,GET_X_LPARAM(lParam),GET_Y_LPARAM(lParam));//获得当前像素颜色
int red = GetRValue(clr);
int green = GetGValue(clr);
int blue = GetBValue(clr);
if(red==0&&green==0&&blue==0)return 0;//-如果本身就是背景的黑色,就不用擦除
//if(clr==0)return 0;//更快速的判断,黑色的三个分量都是0,合起来还是0
COLORREF clrClear = RGB(0,0,0);//合成创建一个黑色
//循环设置25个像素大小的橡皮擦,从中心点(当前鼠标光标所在的点)向四周延伸两个像素
for (int i=-10;i<=10;i++)
{
for (int j=-10;j<=10;j++)
{
SetPixel(hdc,GET_X_LPARAM(lParam)+i,GET_Y_LPARAM(lParam)+j,clrClear); //-单像素
}
}
ReleaseDC(hwnd,hdc);
}
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
default:
return DefWindowProc(hwnd, message, wParam, lParam);
}
}
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrev,LPSTR lpCmd,int iShow)
{
TCHAR ClassName[] = _T("MyClass");
TCHAR title1[] = _T("C++技术网http://www.cjjjs.com");
WNDCLASS wndClass;
wndClass.cbClsExtra=0;
wndClass.cbWndExtra=0;
wndClass.hbrBackground= (HBRUSH)GetStockObject(BLACK_BRUSH);
wndClass.hCursor=LoadCursor(NULL,IDC_ARROW);
wndClass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
wndClass.hInstance = hInstance;
wndClass.lpfnWndProc = WinProc;
wndClass.lpszClassName = ClassName;
wndClass.lpszMenuName=NULL;
wndClass.style=CS_HREDRAW|CS_VREDRAW;
if(!RegisterClass(&wndClass))
{
return 0;
}
HWND hwnd = CreateWindow(ClassName,title1,WS_OVERLAPPEDWINDOW,0,0,440,400,NULL,NULL,hInstance,NULL);
ShowWindow(hwnd,SW_SHOWNORMAL);
MSG msg;
while (GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
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