Bresenham 中点画圆算法实现

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在此记录Bresenham 中点画圆算法，下面直接给出步骤与算法，步骤从计算机图形学一书中截取的，此算法原理在此不做说明，可自行查看计算机图形学一书相关描述。
一、步骤描述
步骤说明

二、代码实现，以OC为开发语言

//以点为类的头文件@interface ScreenPT : NSObject{    GLint x,y;}@property (nonatomic,assign) GLint x;@property (nonatomic,assign) GLint y;-(void) setCoordX:(GLint)x Y:(GLint)y;-(void) incrementX;-(void) decrementY;@end//类的实现文件#import "ScreenPT.h"@implementation ScreenPT@synthesize x;@synthesize y;-(id) init{    if (self = [super init]) {        x = 0;        y = 0;    }    return self;}-(void) setCoordX:(GLint)x Y:(GLint)y{    self.x = x;    self.y = y;}-(void) incrementX{    self.x++;}-(void) decrementY{    self.y--;}@end//实现文件及相关辅助方法void setPixel(GLint x,GLint y){    glBegin(GL_POINTS);    glVertex2i(x, y);    glEnd();}//MARK: Bresenham 中点画圆算法void circleMidpoint(){    GLint xc = 100,yc = 100,radius = 30;//圆心与半径    ScreenPT* spt = [[ScreenPT alloc] init];    GLint p = 1 - radius;    [spt setCoordX:0 Y:radius];    glClear(GL_COLOR_BUFFER_BIT);    glColor3f(0.5, 1.0, 0.0);    void circlePlotPoints(GLint,GLint,ScreenPT*);    circlePlotPoints(xc, yc, spt);    while (spt.x < spt.y) {        [spt incrementX];        if (p < 0) {            p += 2 * spt.x + 1;        } else {            [spt decrementY];            p += 2 * (spt.x - spt.y) + 1;        }        circlePlotPoints(xc, yc, spt);    }    glFlush();}void circlePlotPoints(GLint xc,GLint yc,ScreenPT* spt){    setPixel(xc + spt.x, yc + spt.y);    setPixel(xc - spt.x, yc + spt.y);    setPixel(xc + spt.x, yc - spt.y);    setPixel(xc - spt.x, yc - spt.y);    setPixel(xc + spt.y, yc + spt.x);    setPixel(xc - spt.y, yc + spt.x);    setPixel(xc + spt.y, yc - spt.x);    setPixel(xc - spt.y, yc - spt.x);}

三、效果图

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