屏幕上两点画线+DDALine算法

 1 #include "stdafx.h"
 2 #include"graphics.h"
 3 
 4 void DDALine(int x0, int y0, int x1, int y1);
 5 void main()
 6 {
 7 
 8     int x0, y0, x1, y1;
 9         initgraph(640, 480);    //初始化图形界面,窗口分辨率设置为640*480
10         MOUSEMSG m;        // 定义鼠标消息
11 
12     while (true)
13     {
14         
15         flag:                //重置开始
16         m = GetMouseMsg();// 获取一次鼠标消息
17         switch (m.uMsg)
18         {
19         case WM_LBUTTONDOWN:x0 = m.x; y0 = m.y;    //鼠标第一次按下时，得到坐标（x0,y0）
20             while (true)
21             {
22                 m = GetMouseMsg();// 获取一条鼠标消息
23                 switch (m.uMsg)
24                 {
25                 case WM_LBUTTONDOWN:x1 = m.x; y1 = m.y;//鼠标第二次按下时,得到坐标（x1,y1）
26                     DDALine(x0, y0, x1, y1);
27                     goto flag;   //跳回到flag处进行重置
28                     break;
29                 case WM_RBUTTONUP:
30                     return;    // 按鼠标右键退出程序
31                 }
32             }
33             break;
34         case WM_RBUTTONUP:
35             return;    // 按鼠标右键退出程序
36         }
37     }
38 
39 }
40 
41 void DDALine(int x0, int y0, int x1, int y1) 
42 
43 {
44     int dx = x1 - x0, dy = y1 - y0, k;
45     double x = x0, y = y0, xIncre, yIncre, espl;
46     espl = abs(dy);
47     if (abs(dx) > abs(dy))    
48         espl = abs(dx);
49     xIncre = 1.0*dx / espl;
50     yIncre = 1.0*dy / espl;
51     for (k = 0; k < espl; k++)
52     {
53         putpixel((int)x, (int)y,WHITE);
54         x += xIncre;
55         y += yIncre;
56     }
57 }