计算机图形学直线的生成算法

1、实验二 直线段生成绘制的实现算法班级 08信计2班 学号20080502050姓名 张玉凤 分数 一、实验目的和要求：1、掌握光栅图形显示基本原理2、熟悉直线的生成算法，掌握直线的绘制3、初步了解Tc下画图基本程序结构；4、初步了解DDA画线算法及Bresenham算法的思想和基本方法二、实验主要思想：1、DDA算法思想： 数值微分法即DDA法，这是一种基于直线的微分方程来生成直线的方法。选定和中较大者作为步进方向，取该方向上的为一个像素单位长，即x每次递增一个像素，然后利用公式计算出相应的y值，把每次计算出的取整后顺序输出到显示器，则得到光栅后的直线。2、中点直线算法思想： 假定直线斜率k在

2、01之间(k的其它取值可以类似处理)，当前象素点为（xp,yp），则下一个象素点有两种可选择点P1（xp+1,yp）或P2（xp+1,yp+1）。若P1与P2的中点（xp+1,yp+0.5）称为M，Q为理想直线与x=xp+1垂线的交点。当M在Q的下方时，则取P2应为下一个象素点；当M在Q的上方时，则取P1为下一个象素点。这就是中点画线法的基本原理。三、实验内容及步骤1、dda画线算法画一段直线实验代码：#include"stdio.h"#include"graphics.h"void DDALine(int x1,int y1, int x2,int y

3、2)    double dx, dy,e,x,y;    int i;    dx=x2-x1;    dy=y2-y1;    e=(fabs(dx)>fabs(dy)? fabs(dx):fabs(dy);    dx/=e;    dy/=e;    x=x1;    y=y1;   

4、 for(i=1;i<=e;i+)           putpixel(int)(x+0.5),(int)(y+0.5),GREEN);        x+=dx;        y+=dy;    void main()    int driver=VGA;    in

5、t mode=VGAHI;    initgraph(&driver,&mode,"");    DDALine(100,150,250,300 );    getch();    closegraph();运行结果： 2. 用Bresenham画线算法画直线,并完善算法功能,使之适应更广实验代码：#include<stdio.h>#include<graphics.h>void Bresenhamline(int

6、x1,int y1,int x2,int y2)    int x,y,dx,dy,p;    x=x1;    y=y1;    dx=x2-x1;    dy=y2-y1;    p=2*dy-dx;    for(;x<=x2;x+)            putpixel(x

7、,y,BLUE);        if(p>=0)                    y+;           p+=2*(dy-dx);         &

8、#160;      else                    p+=2*dy;            main()    int driver=VGA;    int mode=VGAHI; 

9、   initgraph(&driver,&mode,"");    Bresenhamline(50,150,200,250);    getch();    closegraph();运行结果：3.、对比Bresenham算法、DDA算法、中点算法三种算法的像素逼近效果和程序执行速度 三两种算法的像素逼近效果和程序执行速度。实验代码：#include <stdio.h>#include <graphics.h>#inclu

10、de <math.h>#include <bios.h>#include <time.h>#include <conio.h>void DrawZb();void BLine(int, int, int, int);void DDALine(int, int, int, int);void MidLine(int, int, int, int);void main() int i; char str20; long oldtime, newtime,time; int gd = VGA, gm = VGAHI; initgraph(&gd

11、, &gm, "D:TCTCPPBGI"); DrawZb(); outtextxy(10,10,"Welcome to this program!"); settextstyle(2,0,0); outtextxy(10,420,"Name : Lineswork 1.0"); outtextxy(10,430,"Information : Computer Graphics Work - lines"); outtextxy(10,440,"CopyRight : (C) Lewsn 2010

12、"); outtextxy(10,450,"Made by : Zhang Shaolei OUC 2010/12 "); settextstyle(0,0,0); setcolor(11); outtextxy(10,30,"Press to Bline! "); getch(); oldtime = biostime(0,0L); for(i = 0; i < 200; i+) BLine(0, 0, 200, 50); BLine(0, 0, 50, 200); BLine(0, 0, -50, 200); BLine(0, 0,

13、-200, 50); BLine(0, 0, -200, -50); BLine(0, 0, -50, -200); BLine(0, 0, 50, -200); BLine(0, 0, 200, -50); newtime = biostime(0,0L); time = (newtime - oldtime) * 1000 /CLK_TCK; sprintf(str, "Time: %d ms",time); outtextxy(170, 30, str); setcolor(10); outtextxy(10, 50, "Press to DDAline!

14、"); getch(); oldtime = biostime(0,0L); for(i = 0; i < 200; i+) DDALine(0, 0, 190, 80); DDALine(0, 0, 80, 190); DDALine(0, 0, -80, 190); DDALine(0, 0, -190, 80); DDALine(0, 0, -190, -80); DDALine(0, 0, -80, -190); DDALine(0, 0, 80, -190); DDALine(0, 0, 190, -80); newtime = biostime(0,0L); tim

15、e = (newtime - oldtime) * 1000 /CLK_TCK; sprintf(str, "Time: %d ms",time); outtextxy(170, 50, str); setcolor(12); outtextxy(10, 70, "Press to Midline! "); getch(); oldtime = biostime(0,0L); for(i = 0; i < 200; i+) MidLine(0, 0, 180, 100); MidLine(0, 0, 100, 180); MidLine(0, 0,

16、 -100, 180); MidLine(0, 0, -180, 100); MidLine(0, 0, -180, -100); MidLine(0, 0, -100, -180); MidLine(0, 0, 100, -180); MidLine(0, 0, 180, -100); newtime = biostime(0,0L); time = (newtime - oldtime) * 1000 /CLK_TCK ; sprintf(str, "Time: %d ms",time); outtextxy(170, 70, str); setcolor(14); g

17、etch(); setcolor(15); outtextxy(10,110,"Press to Exit! "); getch(); closegraph();void DrawZb() setcolor(15); line(320,10,320,470); line(20,240,620,240); line(320,10,315,15); line(320,10,325,15); line(615,235,620,240); line(615,245,620,240); return;void BLine(int x1, int y1, int x2, int y2)

18、 int i, e, exchange, xsign, ysign; int x, y, dx, dy; dx=abs(x2-x1); dy=abs(y2-y1); x=x1; y=y1; exchange=0; if(dy>dx) i=dx; dx=dy; dy=i; exchange=1; e=2*dy-dx; xsign=(x2>x1)? 1:-1; ysign=(y2>y1)? 1:-1; for(i=0; i<=dx; i+) putpixel(x+320, 240-y, 11); if(e>=0) e=e-2*dx; if(exchange) x+=x

19、sign; else y+=ysign; e=e+2*dy; if(exchange) y+=ysign; else x+=xsign; void DDALine(int x1,int y1,int x2,int y2) float x,y,dx,dy; int i,step; x = x1 + 0.5; y = y1 + 0.5; step = abs(x2 - x1) > abs(y2 - y1) ? abs(x2 - x1) : abs(y2 - y1); dx = (float)(x2 - x1) / step; dy = (float)(y2 - y1) / step; for(i = 0; i<=step; i+) putpixel( (int)x+320, 240-(int)y, 10); x += dx; y += dy; void MidLine(int x1, int y1, int x2, int y2) if(abs(x1 - x2) <= 1 && abs(y1 - y2) <= 1) putpixel ( (int)(320 + (x1 + x2)/2 +0.5), (int)(