Bresenham算法画直线（Dev C++）

最近上课在学计算机图形学，第一个实验是用Bresenham算法画直线（可画出各种长度、宽度、斜率的直线），代码如下：

#include <winbgim.h>
#include <conio2.h>
#include <cmath>

void lineBres(int x0,int y0,int xend,int yend,unsigned int width);

int main()
{
     initwindow(640,480); //open a 640x480 graphics window 
   

    lineBres(320,240,400,460,2);
    lineBres(320,240,520,440,2);
    lineBres(320,240,520,400,2);
    lineBres(320,240,520,240,2);
    lineBres(320,240,350,190,2);
    lineBres(320,240,560,0,2);
    lineBres(320,240,520,200,2);
    lineBres(320,240,320,20,2);
    lineBres(320,240,20,40,2);
    lineBres(320,240,120,40,2);
    lineBres(320,240,130,190,2);
    lineBres(320,240,50,240,2);
    lineBres(320,240,50,270,2);
    lineBres(320,240,90,470,2);
    lineBres(320,240,20,480,2);
    lineBres(320,240,320,440,2);
   
   
     getch();   //wait for user to press a key
     closegraph();        //close graphics window
     return 0;
}

void lineBres(int x0,int y0,int xend,int yend,unsigned int width)
{
         int dx = fabs(xend - x0),dy = fabs(yend - y0);
         int p = 2 * dy - dx;
         int c1 = 2 * dy, c2 = 2 * (dy - dx);
         int x,y;
        
        
         //特殊情况 :平行于Y轴
         if(x0 == xend)
           {
               int temp = y0>yend?yend:y0;
      
               for(int i = 0;i < dy; i++,temp++)
                   for(int j = 0; j < width ; j++)     
                           putpixel(x0 + j,temp,RGB(0,255,0));   
              
               return;   
           }   
        
        double k =double(yend - y0) / double(xend - x0);
         if(x0 > xend)
               {
                      x = xend;
                      y = yend;
                      xend = x0;      
               }
         else
               {
                      x = x0;
                      y = y0;      
               }
         
         if(k != 0)    
              for(int i = 0; i < width ; i++)     
                       putpixel(x + i,y,RGB(0,255,0));
         else
              for(int i = 0; i < width ; i++)     
                       putpixel(x,y + i,RGB(0,255,0));
         while(x < xend)
                 {
                        x++;
                        if(p < 0)
                             {
                                 p += c1;
                                
                             }
                        else
                            {
                                 if(k>=0 && k <=1)
                                        y++;
                                 else if(k > 1)
                                        y += (k + 0.5);                                       
                                 else if(k<0 && k>=-1)
                                        y--;
                                 else if( k < -1)
                                        y += (k-0.5);
                                 p += c2;
                             }

                        if(k != 0)    
                                for(int i = 0; i < width ; i++)     
                                        putpixel(x + i,y,RGB(0,255,0));
                        else
                                for(int i = 0; i < width ; i++)     
                                        putpixel(x,y + i,RGB(0,255,0));
                 }
}