4

Im using de DDA (Digital Diferential Analizer) to make a line, and thought I know maybe using de DrawLine the way I am, just run along with it. Im trying to make different types of lines like dashed or dotted, etc. Im thinking in makeing the for from below jump some numbers to make a dotted line. But I cant still find a way todo it. This is what I have so far:

public void paint(Graphics g) {
        super.paint(g);
        int dot=0;
        int x1 = pointStart.x;
        int x2 = pointEnd.x;
        int y1 = pointStart.y;
        int y2 = pointEnd.y;
        float dx, dy, m, y, x;
        if (x1>x2){
            int ax = x2;
            int ay = y2;
            x2 = x1;
            x1 = ax;
            y2 = y1;
            y1 = ay;
        }
        dx = x2 - x1;
        dy = y2 - y1;
        m = dy/dx;
        if (m>=-1&&m<=1){
            dot = (int)dx/4;
            y = y1;
            System.out.println(m);
            for (x = x1 ; x <= x2;x++){
                //if (x>=dot&&x<=dot+10||x>=dot*2&&x<=dot*2+10||x>=dot*3&&x<=dot*3+10){
                    g.drawLine((int)x, (int)Math.round(y), (int)x, (int)Math.round(y));
                    y+=m;
                //}
            }   
        }
        else{
            x = x1;
            System.out.println(m);
            for (y = y1 ; y <= y2;y++){
                g.drawLine((int)Math.round(x), (int)y, (int)Math.round(x), (int)y);
                x+=1/m; 
            }
        }

        /*if (pointStart != null) {
            if (x1>)        
            g.setColor(Color.RED);
            //g.drawLine(pointStart.x, pointStart.y, pointEnd.x, pointEnd.y);
            g.drawLine(x1, y1, x1, y1);
        }*/

    }

Any ideas?

4

1 回答 1

1
  1. 你需要画线功能（在你的情况下 g.drawline(x0,y0,x1,y1); ）。
  2. 不在乎颜​​色（以后可以玩）
  3. 你需要定义你的模式（线条和空格的大小，以像素为单位）
  4. 例如 int pattern[]={10,-5,0} （10px 行，然后 5px 空间，0 表示从头开始重复）... - 值是空格 + 值是行
  5. 您需要“全局”状态（模式中的实际索引和绘制的实际像素长度），您也可以拥有全局模式指针或将所有内容封装在类/结构中。

好的，所以基本思想是将任何线分割为选定的模式，例如：

//---------------------------------------------------------------------------
// pattern draw state
int    _pattern_ix=0; // actual index in pattern need to reset it to zero before any pattern change
double _pattern_l=0;  // already drawed or skipped pixels from actual pattern[_pattern_ix]
// predefined patterns
int    _pattern_dash_dash[]={ 10,-10,        0 };
int    _pattern_dash_dot[] ={ 10,- 5,  1,- 5,0 };
int    _pattern_dot_dot[]  ={  1,- 5,        0 };
//---------------------------------------------------------------------------
// draw line function
void drawline(int x0,int y0,int x1,int y1)
    {
    // this is just borland GDI access to draw line function
    Form1->Canvas->MoveTo(x0,y0);
    Form1->Canvas->LineTo(x1,y1);
    }
//---------------------------------------------------------------------------
void pattern_line(int x0,int y0,int x1,int y1,int *pattern)
    {
    int p;
    double x,y,xx,yy,dx,dy,dl,t,dt;
    dx=x1-x0;
    dy=y1-y0;
    dl=sqrt((dx*dx)+(dy*dy));
    dx/=dl; dy/=dl;
    for (t=0.0,dt=0.0;dl>=0.5;)
        {
        p=pattern[_pattern_ix];
        if (p<0) // skip
            {
            dt=-p-_pattern_l;                      // t=space to skip [px]
            if (dt>dl) { _pattern_l+=dl; return; } // space is bigger then rest of line
            dl-=dt; t+=dt; _pattern_l=0.0;         // update line params and continue to next pattern entry
            }
        else     // draw
            {
            dt=+p-_pattern_l;                     // t=space to draw [px]
            x=x0+double(t*dx);                    // actual point pos
            y=y0+double(t*dy);                    // space is bigger then rest of line
            if (dt>dl) { _pattern_l+=dl; drawline(x,y,x1,y1); return; }
            dl-=dt; t+=dt; _pattern_l=0.0;        // update line params
            xx=x0+double(t*dx);                   // actual point pos
            yy=y0+double(t*dy);
            drawline(x,y,xx,yy);                  // draw line and continue to next pattern entry
            }
        _pattern_ix++;
        if (!pattern[_pattern_ix]) _pattern_ix=0;
        }
    }
//---------------------------------------------------------------------------
void main()
    {
    // borland GDI clear screen and color settings
    Canvas->Brush->Color=clBlack;
    Canvas->Pen->Color=clWhite;
    Canvas->FillRect(ClientRect);
    // draw dash-dot-ed rectangle
    int x0,x1,y0,y1;
    x0=30; x1=200;
    y0=30; y1=100;
    pattern_line(x0,y0,x1,y0,_pattern_dash_dot);
    pattern_line(x1,y0,x1,y1,_pattern_dash_dot);
    pattern_line(x1,y1,x0,y1,_pattern_dash_dot);
    pattern_line(x0,y1,x0,y0,_pattern_dash_dot);
    }
//---------------------------------------------------------------------------

并且不要忘记在任何模式样式更改之前将模式 ix,l 重置为零。代码没有优化，所以它很慢，但我希望很容易理解。

于 2013-09-05T18:36:00.753 回答