计算机图形学:3种画直线算法（转）

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计算机图形学：3种画直线算法

分类:C/C++

//---------------------------------------------------------------------
//绘制直线的DDA算法基本函数
//---------------------------------------------------------------------
void LineDDA(int x0,int y0,int x1,int y1,int color,HDC hdc)
{
float dy,dx,x,y,m;
dx=x1-x0;
dy=y1-y0;
m=dy/dx;
if(x0<x1)
{
if(m<=1&&m>=-1)
{
y=y0;
for(x=x0;x<=x1;x++)
{
SetPixel(hdc,x,int(y+0.5),color);
y+=m;
}
}
}
if(x0>x1)
{
if(m<=1&&m>=-1)
{
y=y0;
for(x=x0;x>=x1;x--)
{
SetPixel(hdc,x,int(y+0.5),color);
y-=m;
}
}
}
if(y0<y1)
{
if(m>=1||m<=-1)
{
m=1/m;
x=x0;
for(y=y0;y<=y1;y++)
{
SetPixel(hdc,int(x+0.5),y,color);
x+=m;
}
}
}
if(y0>y1)
{
if(m<=-1||m>=1)
{
m=1/m;
x=x0;
for(y=y0;y>=y1;y--)
{
SetPixel(hdc,int(x+0.5),y,color);
x-=m;
}
}
}
}
//---------------------------------------------------------------------
//DDA算法对应的演示功能函数
//---------------------------------------------------------------------
void LineDDA_Demo(int x0,int y0,int x1,int y1,int color,HDC hdc,bool demo)
{
float dy,dx,x,y,m,Time;
Time=timeGetTime();
dx=x1-x0;
dy=y1-y0;
m=dy/dx;
if(x0<x1)
{
if(m<=1&&m>=-1)
{
y=y0;
for(x=x0;x<=x1;x++)
{
BitBlt(hdc,x*10,int(y+0.5)*10,10,10,MemDC,0,0,SRCCOPY);
y+=m;
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
if(x0>x1)
{
if(m<=1&&m>=-1)
{
y=y0;
for(x=x0;x>=x1;x--)
{
BitBlt(hdc,x*10,int(y+0.5)*10,10,10,MemDC,0,0,SRCCOPY);
y-=m;
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
if(y0<y1)
{
if(m>=1||m<=-1)
{
m=1/m;
x=x0;
for(y=y0;y<=y1;y++)
{
BitBlt(hdc,int(x+0.5)*10,y*10,10,10,MemDC,0,0,SRCCOPY);
x+=m;
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
if(y0>y1)
{
if(m<=-1||m>=1)
{
m=1/m;
x=x0;
for(y=y0;y>=y1;y--)
{
BitBlt(hdc,int(x+0.5)*10,y*10,10,10,MemDC,0,0,SRCCOPY);
x-=m;
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
}以上代码仅供参考,编程环境VC.NET,希望能给还没有任何思路的同学一点帮助,完整源文件不提供,请勿开口索要。

//---------------------------------------------------------------------
//绘制直线的中点算法基本函数
//---------------------------------------------------------------------
void LineMID(int x0,int y0,int x1,int y1,int color,HDC hdc)
{
float dx,dy,incrE,incrNE,d,x,y,m;
if(true)
{
dx=x1-x0;
if(x0>x1)
dx=-dx;
dy=y1-y0;
if(y0>y1)
dy=-dy;
m=dy/dx;
d=dx-2*dy;
incrE=-2*dy;
incrNE=2*(dx-dy);
x=x0,y=y0;
SetPixel(hdc,x,y,color);
if(m<=1&&m>=-1)
{
if(x0<x1)
{
while(x<x1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
y++;
}
x++;
if(y0<y1)
SetPixel(hdc,x,y,color);
if(y0>=y1)
SetPixel(hdc,x,(2*y0-y),color);
}
}
if(x0>=x1)
{
while(x>x1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
y++;
}
x--;
if(y0<y1)
SetPixel(hdc,x,y,color);
if(y0>=y1)
SetPixel(hdc,x,(2*y0-y),color);
}
}
}
if(m<-1||m>1)
{
dx=x1-x0;
if(x0>x1)
dx=-dx;
dy=y1-y0;
if(y0>y1)
dy=-dy;
d=dy-2*dx; //与斜率小于1时候的情况相比，dx与dy的值刚好互换
incrE=-2*dx;
incrNE=2*(dy-dx);
x=x0,y=y0;
if(y0<y1)
{
while(y<y1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
x++;
}
y++;
if(x0<x1)
SetPixel(hdc,x,y,color);
if(x0>=x1)
SetPixel(hdc,(2*x0-x),y,color);
}
}
if(y0>=y1)
{
while(y>y1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
x++;
}
y--;
if(x0<x1)
SetPixel(hdc,x,y,color);
if(x0>=x1)
SetPixel(hdc,(2*x0-x),y,color);
}
}
}
}
}
//---------------------------------------------------------------------
//中点算法对应的演示功能函数
//---------------------------------------------------------------------
void LineMID_Demo(int x0,int y0,int x1,int y1,int color,HDC hdc,bool demo)
{
float dx,dy,incrE,incrNE,d,x,y,m,Time;
Time=timeGetTime();
if(true)
{
dx=x1-x0;
if(x0>x1)
dx=-dx;
dy=y1-y0;
if(y0>y1)
dy=-dy;
m=dy/dx;
d=dx-2*dy;
incrE=-2*dy;
incrNE=2*(dx-dy);
x=x0,y=y0;
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(m<=1&&m>=-1)
{
if(x0<x1)
{
while(x<x1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
y++;
}
x++;
if(y0<y1)
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(y0>=y1)
BitBlt(hdc,x*10,(2*y0-y)*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
if(x0>=x1)
{
while(x>x1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
y++;
}
x--;
if(y0<y1)
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(y0>=y1)
BitBlt(hdc,x*10,(2*y0-y)*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
if(m<-1||m>1)
{
dx=x1-x0;
if(x0>x1)
dx=-dx;
dy=y1-y0;
if(y0>y1)
dy=-dy;
d=dy-2*dx;
incrE=-2*dx;
incrNE=2*(dy-dx);
x=x0,y=y0;
if(y0<y1)
{
while(y<y1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
x++;
}
y++;
if(x0<x1)
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(x0>=x1)
BitBlt(hdc,(2*x0-x)*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
if(y0>=y1)
{
while(y>y1)
{
if(d>0)
d+=incrE;
else
{
d+=incrNE;
x++;
}
y--;
if(x0<x1)
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(x0>=x1)
BitBlt(hdc,(2*x0-x)*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
}
}

//---------------------------------------------------------------------

bresenham算法是计算机图形学中为了“显示器（屏幕或打印机）系由像素构成”的这个特性而设计出来的算法，使得在求直线各点的过程中全部以整数来运算，因而大幅度提升计算速度

Bresenham算法是计算机图形学领域使用最广泛的直线扫描转换方法。原理是：

　　过各行、各列像素中心构造一组虚拟网格线，按直线从起点到终点的顺序计算直线各垂直网格线的交点，然后确定该列像素中与此交点最近的像素。该算法的优点在于可以采用增量计算，使得对于每一列，只要检查一个误差项的符号，就可以确定该列所求的像

//绘制直线的Bresenham算法基本函数

//---------------------------------------------------------------------void LineBRE(int x0,int y0,int x1,int y1,int color,HDC hdc)
{
float dy,dx,x,y,m,d;
dx=x1-x0;
if(x1<x0)
dx=-dx;
dy=y1-y0;
if(y1<y0)
dy=-dy;
m=dy/dx;
d=-dx;
x=x0,y=y0;
if(x0<x1)
{
if(m<=1&&m>=-1)
{
for(x=x0;x<=x1;x++)
{
if(d>=0)
{
y++;
d-=2*dx;
}
d+=2*dy;
if(y1<y0)
SetPixel(hdc,x,(2*y0-y),color);
else
SetPixel(hdc,x,y,color);
}
}
}
if(x0>=x1)
{
if(m<=1&&m>=-1)
{
for(x=x0;x>=x1;x--)
{
if(d>=0)
{
y++;
d-=2*dx;
}
d+=2*dy;
if(y1<y0)
SetPixel(hdc,x,(2*y0-y),color);
else
SetPixel(hdc,x,y,color);
}
}
}
if(y0<y1)
{
if(m<-1||m>1)
{
for(y=y0;y<=y1;y++)
{
if(d>=0)
{
x++;
d-=2*dy;
}
d+=2*dx;
if(x1<x0)
SetPixel(hdc,(2*x0-x),y,color);
else
SetPixel(hdc,x,y,color);
}
}
}
if(y0>=y1)
{
if(m<-1||m>1)
{
for(y=y0;y>=y1;y--)
{
if(d>=0)
{
x++;
d-=2*dy;
}
d+=2*dx;
if(x1<x0)
SetPixel(hdc,(2*x0-x),y,color);
else
SetPixel(hdc,x,y,color);
}
}
}
}
//---------------------------------------------------------------------
//Bresenham算法对应的演示功能函数
//---------------------------------------------------------------------
void LineBRE_Demo(int x0,int y0,int x1,int y1,int color,HDC hdc,bool demo)
{
float dy,dx,x,y,m,d,Time;
Time=timeGetTime();
dx=x1-x0;
if(x1<x0)
dx=-dx;
dy=y1-y0;
if(y1<y0)
dy=-dy;
m=dy/dx;
d=-dx;
x=x0,y=y0;
if(x0<x1)
{
if(m<=1&&m>=-1)
{
for(x=x0;x<=x1;x++)
{
if(d>=0)
{
y++;
d-=2*dx;
}
d+=2*dy;
if(y1<y0)
BitBlt(hdc,x*10,(2*y0-y)*10,10,10,MemDC,0,0,SRCCOPY);
else
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
if(x0>=x1)
{
if(m<=1&&m>=-1)
{
for(x=x0;x>=x1;x--)
{
if(d>=0)
{
y++;
d-=2*dx;
}
d+=2*dy;
if(y1<y0)
BitBlt(hdc,x*10,(2*y0-y)*10,10,10,MemDC,0,0,SRCCOPY);
else
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
if(y0<y1)
{
if(m<-1||m>1)
{
for(y=y0;y<=y1;y++)
{
if(d>=0)
{
x++;
d-=2*dy;
}
d+=2*dx;
if(x1<x0)
BitBlt(hdc,(2*x0-x)*10,y*10,10,10,MemDC,0,0,SRCCOPY);
else
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
if(y0>=y1)
{
if(m<-1||m>1)
{
for(y=y0;y>=y1;y--)
{
if(d>=0)
{
x++;
d-=2*dy;
}
d+=2*dx;
if(x1<x0)
BitBlt(hdc,(2*x0-x)*10,y*10,10,10,MemDC,0,0,SRCCOPY);
else
BitBlt(hdc,x*10,y*10,10,10,MemDC,0,0,SRCCOPY);
if(demo)
{
while((timeGetTime()-Time)<delay)
int a=1;
}
Time=timeGetTime();
}
}
}
}

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