基于 的多边形裁剪算法的实现
一、新建 项目
此处就不再赘述,没有 基础的可以先看第一个 程序。设置项目名为 。【注】:以下没有特殊说明的,均在 文件下编程。
二、宏定义设置
在适当位置设置宏。
#define LEFT 1
#define RIGHT 2
#define BOTTOM 4
#define TOP 8
#define XL 100
#define XR 300
#define YT 150
#define YB 300
三、全局变量初始化
在适当位置设置全局变量。
const UINT N = 8;
CPoint pt[N], pts[N], ptse[N], p[N], ptset1[N];
int flag=0;
三、窗口初始化
void CPolygonClippingView::OnDraw(CDC* pDC)
{
CPolygonClippingDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;
// TODO: 在此处为本机数据添加绘制代码
CPen newpen(PS_SOLID, 1, RGB(255, 0, 0));
CPen *old = pDC->SelectObject(&newpen);
pDC->Rectangle(CRect(XL, YT, XR, YB));
ptset1[0] = CPoint(20, 150);
ptset1[1] = CPoint(120, 110);
ptset1[2] = CPoint(250, 150);
ptset1[3] = CPoint(200, 230);
ptset1[4] = CPoint(20, 150);
pDC->TextOutW(0, 50, L"双击鼠标左键 , 出现要剪切的多边形 ");
pDC->SelectObject(old);
}
四、多边形初始化
类向导添加消息中的 处理函数。
void CPolygonClippingView::OnLButtonDblClk(UINT nFlags, CPoint point)
{
// TODO: 在此添加消息处理程序代码和/或调用默认值
CDC* pDC = GetDC();
CPen newpen(PS_SOLID, 1, RGB(0, 0, 0));
CPen *old = pDC->SelectObject(&newpen);
flag = 1;
pDC->MoveTo(ptset1[0]);
for (int i = 1; i < 5; i++)
pDC->LineTo(ptset1[i]);
CView::OnLButtonDblClk(nFlags, point);
}
五、多边形裁剪算法实现
设置 为 ,添加事件处理程序。
void CPolygonClippingView::OnClippolygon()
{
// TODO: 在此添加命令处理程序代码
CDC* pDC = GetDC();
CPen newpen(PS_SOLID, 1, RGB(0, 0, 0));
CPen *old = pDC->SelectObject(&newpen);
if (flag != 1)
{
MessageBox(L"请先双击鼠标左键", L"警告!");
}
else
{
int i, k;
int code1, code2;
int M = 5;
RedrawWindow();
k = 0;
for (i = 0; i < M; i++)
{
int c = 0;
if (ptset1[i].x < XL)
c = 1;
else if (ptset1[i].x > XL)
c = 0;
code1 = c;
c = 0;
if (ptset1[i + 1].x < XL)
c = 1;
else if (ptset1[i + 1].x > XL)
c = 0;
code2 = c;
if (code1 != 0 && code2 == 0)
{
pt[k].x = XL;
pt[k].y = ptset1[i].y + (ptset1[i + 1].y - ptset1[i].y)*(XL - ptset1[i].x) / (ptset1[i + 1].x - ptset1[i].x);
pt[k + 1].x = ptset1[i + 1].x;
pt[k + 1].y = ptset1[i + 1].y;
k = k + 2;
}
if (code1 == 0 && code2 == 0)
{
if (k == 0)
{
pt[k].x = ptset1[i].x;
pt[k].y = ptset1[i].y;
pt[k + 1].x = ptset1[i + 1].x;
pt[k + 1].y = ptset1[i + 1].y;
k = k + 2;
}
else
{
pt[k].x = ptset1[i + 1].x;
pt[k].y = ptset1[i + 1].y;
k = k + 1;
}
}
if (code1 == 0 && code2 != 0)
{
pt[k].x = XL;
pt[k].y = ptset1[i].y + (ptset1[i + 1].y - ptset1[i].y)*(XL - ptset1[i].x) / (ptset1[i + 1].x - ptset1[i].x);
k++;
}
}
pt[k].x = pt[0].x;
pt[k].y = pt[0].y;
M = k + 1;
k = 0;
for (i = 0; i < M; i++)
{
int c = 0;
if (pt[i].x < XR)
c = 0;
else if (pt[i].x > XR)
c = 2;
code1 = c;
c = 0;
if (pt[i + 1].x < XR)
c = 0;
else if (pt[i + 1].x > XR)
c = 2;
code2 = c;
if (code1 == 0 && code2 == 0)
{
if (k == 0)
{
pts[k].x = pt[i].x;
pts[k].y = pt[i].y;
pts[k + 1].x = pt[i + 1].x;
pts[k + 1].y = pt[i + 1].y;
k = k + 2;
}
else
{
pts[k].x = pt[i + 1].x;
pts[k].y = pt[i + 1].y;
k++;
}
}
if (code1 != 0 && code2 == 0)
{
pts[k].x = XR;
pts[k].y = pt[i].y + (pt[i + 1].y - pt[i].y)*(XR - pt[i].x) / (pt[i + 1].x - pt[i].x);
pts[k + 1].x = pt[i + 1].x;
pts[k + 1].y = pt[i + 1].y;
k = k + 2;
}
}
if (code1 == 0 && code2 != 0)
{
pts[k].x = XR;
pts[k].y = pt[i].y + (pt[i + 1].y - pt[i].y)*(XR - pt[i].x) / (pt[i + 1].x - pt[i].x);
k = k + 1;
}
pts[k] = pts[0];
M = k + 1;
k = 0;
for (i = 0; i < M; i++)
{
int c = 0;
if (pts[i].y > YB)
c = 4;
else if (pts[i].y < YB)
c = 0;
code1 = c;
c = 0;
if (pts[i + 1].y > YB)
c = 4;
else if (pts[i + 1].y < YB)
c = 0;
code2 = c;
if (code1 == 0 && code2 == 0)
{
if (k == 0)
{
ptse[k].x = pts[i].x;
ptse[k].y = pts[i].y;
ptse[k + 1].x = pts[i + 1].x;
ptse[k + 1].y = pts[i + 1].y;
k = k + 2;
}
else
{
ptse[k].x = pts[i + 1].x;
ptse[k].y = pts[i + 1].y;
k = k + 1;
}
}
if (code1 != 0 && code2 == 0)
{
ptse[k].y = YB;
ptse[k].x = pts[i].x + (pts[i + 1].x - pts[i].x)*(YB - pts[i].y) / (pts[i + 1].y - pts[i + 1].y);
ptse[k + 1].x = pts[i + 1].x;
ptse[k + 1].y = pts[i + 1].y;
k = k + 2;
}
}
if (code1 == 0 && code2 != 0)
{
ptse[k].y = YB;
ptse[k].x = pts[i].x + (pts[i + 1].x - pts[i].x)*(YB - pts[i].y) / (pts[i + 1].y - pts[i + 1].y);
k = k + 1;
}
ptse[k] = ptse[0];
M = k + 1;
k = 0;
for (i = 0; i < M; i++)
{
int c = 0;
if (ptse[i].y > YT)
c = 0;
else if (ptse[i].y < YT)
c = 1;
code1 = c;
c = 0;
if (ptse[i + 1].y > YT)
c = 0;
else if (ptse[i + 1].y < YT)
c = 1;
code2 = c;
if (code1 != 0 && code2 == 0)
{
p[k].y = YT;
p[k].x = ptse[i].x + (ptse[i + 1].x - ptse[i].x)*(YT - ptse[i].y) / (ptse[i + 1].y - ptse[i].y);
p[k + 1].x = ptse[i + 1].x;
p[k + 1].y = ptse[i + 1].y;
k = k + 2;
}
if (code1 == 0 && code2 == 0)
{
if (k == 0)
{
p[k].x = ptse[i].x;
p[k].y = ptse[i].y;
p[k + 1].x = ptse[i + 1].x;
p[k + 1].y = ptse[i + 1].y;
k = k + 2;
}
else
{
p[k].x = ptse[i + 1].x;
p[k].y = ptse[i + 1].y;
k = k + 1;
}
}
if (code1 == 0 && code2 != 0)
{
p[k].y = YT;
p[k].x = ptse[i].x + (ptse[i + 1].x - ptse[i].x)*(YT - ptse[i].y) / (ptse[i + 1].y - ptse[i].y);
k++;
}
}
p[k] = p[0];
M = k + 1;
pDC->MoveTo(p[0]);
for (int j = 1; j <= M; j++)
{
pDC->LineTo(p[j]);
}
}
}