void cb_line(int x1,int y1,int x2,int y2)
{
int dx,dy,n,k,i,f;
int x,y;
dx=abs(x2-x1);
dy=abs(y2-y1);
n=dx+dy;
if(x2>=x1)
{
k=y2>=y1?1:4;
x=x1;
y=y1;
}
else
{
k=y2>=y1?2:4;
x=x1;
y=y1;
}
for(i=0,f=0;i<n;i++)
if(f>=0)
switch(k)
{
case 1:putpixel(x++,y,3);f-=dy;break;
case 2:putpixel(x,y++,3);f-=dx;break;
case 3:putpixel(x--,y,3);f-=dy;break;
case 4:putpixel(x,y--,3);f-=dx;break;
}
else
switch(k)
{
case 1:putpixel(x,y++,3);f+=dx;break;
case 2:putpixel(x--,y,3);f+=dy;break;
case 3:putpixel(x,y--,3);f+=dx;break;
case 4:putpixel(x++,y,3);f+=dy;break;
}
}
