lt87.c

programs in <C program design>

# include "stdio.h"
 # include "graphics.h"
 #define X0 100
 #define X1 500
 #define Y0 100
 #define Y1 300
 void  main( )
 {
 	int g_driver,g_mode,g_error;
 	g_driver=VGA;   /* 设置显示模式  */
 	g_mode=VGAHI;
 	initgraph(&g_driver,&g_mode,"");
 	g_error=graphresult();
 	if (g_error<0)
 	   {printf("initgraph error: %s\n",grapherrormsg(g_error));
 	   exit(1);
 	   };
 midpointline(X0,Y0,X1,Y1,YELLOW);
 }
 midpointline(x0,y0,x1,y1,color)
 int x0,y0,x1,y1,color;
 {
 int i,a,b,delta1,delta2,d,x,y;
 a=y0-y1;
 b=x1-x0;
 d=2*a+b;
 delta1=2*a;
 delta2=2*(a+b);
 x=x0;
 y=y0;
while (x<x1)
 {
 if (d<0)
 {x++;y++;
 d+=delta2;
 }
 else
 {
 x++;
 d+=delta1;
 }
 putpixel(x,y,color);  /* 在x,y坐标上画一个颜色为黄色的象点 */
 }
 getchar();
 textmode(180);
 }