[分享]关于画图底层算法 - blueboy82006的博客

作者在 2008-10-03 09:42:52 发布以下内容

这贴加精了,贴这做个纪念...

平时, 用惯了API、CDC和封装好的内部函数,关于画线,画圆这些东西都是信手拈来...
最近学习计算机图形学,不得不深入内部研究一下底层算法...
在这里贴几个代码分享一下!
(这里只给出MFC的OnDraw函数)

一、画线的三个算法：
1。DDA（数值微分）法:

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代码:

void CDDALineView::OnDraw(CDC* pDC)
{
    CDDALineDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    // TODO: add draw code for native data here
    int x,x0(200),y0(200),x1(500),y1(500);
    float dx,dy,y,k;
    dx=x1-x0;
    dy=y1-y0;
    k=dy/dx;
    y=y0;
    for(x=x0;x<=x1;x++)
    {
        pDC->SetPixel(x,(int)(y+0.5),RGB(255,0,0));
        y+=k;
    }
}

2.中点画线算法

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代码:

void CMidpointLineView::OnDraw(CDC* pDC)
{
    CMidpointLineDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    // TODO: add draw code for native data here
    int a,b,d1,d2,d,x,y;
    int x0(200),x1(500),y0(200),y1(500);
    a=y0-y1;
    b=x1-x0;
    d=2*a+b;
    d1=2*a;
    d2=2*(a+b);
    x=x0;
    y=y0;
    pDC->SetPixel(x,y,RGB(0,255,0));
    while(x<x1)
    {
        if(d<0)
        {
            x++;
            y++;
            d+=d2;
        }
        else
        {
            x++;
            d+=d1;
        }
        pDC->SetPixel(x,y,RGB(0,255,0));
    }
}

3。Bresenham算法：

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代码:

void CBresenhamline2View::OnDraw(CDC* pDC)
{
    CBresenhamline2Doc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    // TODO: add draw code for native data here
    int x0(200),y0(200),x1(500),y1(500);
    int x,y,dx,dy;
    dx=x1-x0;
    dy=y1-y0;
    int e=-dx;
    x=x0;
    y=y0;
    for(int i=0;i<=dx;i++)
    {
        pDC->SetPixel(x,y,RGB(0,0,255));
        x=x+1;
        e=e+2*dy;
        if(e>=0)
        {
            y++;
            e=e-2*dx;
        }
    }
}

二、中点画圆算法：

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代码:

void CMidPointCircleView::OnDraw(CDC* pDC)
{
    CMidPointCircleDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    // TODO: add draw code for native data here
    int r=100;            //半径
    int m(300),n(250);    //圆心坐标
    int x,y;
    float d;
    x=0;
    y=0+r;
    d=1.25-r;
    //中点画圆算法

    pDC->SetPixel(m+x,n+y,RGB(255,0,0));
    pDC->SetPixel(m+y,n+x,RGB(255,0,0));
    pDC->SetPixel(m-x,n+y,RGB(255,0,0));
    pDC->SetPixel(m+y,n-x,RGB(255,0,0));
    pDC->SetPixel(m+x,n-y,RGB(255,0,0));
    pDC->SetPixel(m-y,n+x,RGB(255,0,0));
    pDC->SetPixel(m-x,n-y,RGB(255,0,0));
    pDC->SetPixel(m-y,n-x,RGB(255,0,0));
    while(x<=y)
    {
        if(d<0)
            d+=2*x+3;
        else
        {
            d+=2*(x-y)+5;
            y--;
        }
        x++;
        pDC->SetPixel(m+x,n+y,RGB(255,0,0));
        pDC->SetPixel(m+y,n+x,RGB(255,0,0));
        pDC->SetPixel(m-x,n+y,RGB(255,0,0));
        pDC->SetPixel(m+y,n-x,RGB(255,0,0));
        pDC->SetPixel(m+x,n-y,RGB(255,0,0));
        pDC->SetPixel(m-y,n+x,RGB(255,0,0));
        pDC->SetPixel(m-x,n-y,RGB(255,0,0));
        pDC->SetPixel(m-y,n-x,RGB(255,0,0));
    }
}