C语言用Bresenham算法画圆，哪位高手教教，主要是算法里的内容，谢谢！

的确哈，关键在于对delta的理解

可以看到，都是delta=2*(1-radius)这样的，起作用应该是判断要画的点x、y坐标的变化趋势，先把我注释了的代码贴下，加了getch()可以看到画的过程

-----------------------------------------------------------------

#include<graphics.h>

#include<stdio.h>

void BresenhemCircle(int centerx, int centery, int radius, int color, int type)

void main()

{

int drive=DETECT,mode

int i,j

initgraph(&drive,&mode,"")

BresenhemCircle(300,200,100,15,0)

getch()

}

void BresenhemCircle(int centerx, int centery, int radius, int color, int type)

{

int x =type = 0/*初始横坐标为原点*/

int y = radius/*初始纵坐标远离原点*/

int delta = 2*(1-radius)

int direction

while (y >= 0)

{

getch()

if (!type)/*执行*/

{

/*在上半圆画两点*/

putpixel(centerx+x, centery+y, color)

putpixel(centerx-x, centery+y, color)

/*在下半圆画两点*/

putpixel(centerx-x, centery-y, color)

putpixel(centerx+x, centery-y, color)

getch()

}

else/*不执行*/

{

line(centerx+x, centery+y, centerx+x, centery-y)

line(centerx-x, centery+y, centerx-x, centery-y)

getch()

}

/*以下代码设置下次四点的位置，圆是对称的，且此方法相当于同时画四个圆弧

观察右上方圆弧可知，前一半是x增的要快些，后一半是y减的快些*/

if (delta <0)

{

if ((2*(delta+y)-1) <0)

direction = 1/*选择横向加*/

else

direction = 2

}

else if(delta >0)

{

if ((2*(delta-x)-1) >0)

direction = 3/*选择纵向减*/

else

direction = 2

}

else

direction=2

switch(direction)

{

case 1:

x++/*只横坐标远离原点*/

delta += (2*x+1)/*小执行到这，所以加*/

break

case 2:

x++

y--/*横向远离，同时纵向靠近*/

delta += 2*(x-y+1)/*即(2*x+1)+(-2*y+1)*/

break

case 3:

y--/*只纵坐标靠近原点*/

delta += (-2*y+1)/*大执行到这，所以减*/

break

}

}

}

这是我做过的，你试试

#include<stdio.h>

#include<graphics.h>

#define PATH "c:\\TC30\\BGI"

int x0,y0

void Bresenham_Circle(int r,int color)

{

int x,y,delta,delta1,delta2,direction

x=0

y=r

delta=2*(1-r)

while(y>=0)

{

putpixel(x+x0,y+y0,color)

putpixel(x0-x,y0-y,color)

putpixel(x0-x,y+y0,color)

putpixel(x+x0,y0-y,color)

if(delta<0)

{

delta1=2*(delta+y)-1

if(delta1<=0)

direction=1

else

direction=2

}

else

{

if(delta>0)

{

delta2=2*(delta-x)-1

if(delta2<=0)

direction=2

else

direction=3

}

else

direction=2

}

switch(direction)

{

case 1:x++

delta+=2*x+1

break

case 2:x++

y--

delta+=2*(x-y+1)

break

case 3:y--

delta+=(-2*y+1)

break

}

}

}

int main()

{

int a,b

int r,color

// scanf("%d%d%d%d%d%d",&x0,&y0,&x1,&y1,&color)

a=VGA

b=VGAHI

initgraph(&a,&b,PATH)

setbkcolor(24)

setcolor(15)

x0=200

y0=200

r=180

color=10

Bresenham_Circle(r,color)

getch()

return 1

}

---