DDA算法 中点算法

#include "math.h" #include "stdio.h" #include "stdlib.h" #define ESC 0x1b #include "graphics.h" void MidPointLine(int x0,int y0,int x1,int y1,int color) { int dx,dy,incrE,incrNE,d,x,y,m,n; float k; if(x0>x1) { m=x0;x0=x1;x1=m; n=y0;y0=y1;y1=n; } dx=x1-x0; dy=y1-y0; if(x1!=x0) { k=(float)dy/dx; if(k>=0) { if(k<=1) { d=dx-2*dy; incrE=-2*dy; incrNE=2*(dx-dy); x=x0,y=y0; putpixel(x,y,color); while(x<x1) { if(d>0) d+=incrE; else { d+=incrNE; y++; } x++; putpixel(x,y,color); } } else { d=dy-2*dx; incrE=2*dx; incrNE=-2*(dx-dy); x=x0,y=y0; putpixel(x,y,color); while(y<y1) { if(d<0) d+=incrE; else { d+=incrNE; x++; } y++; putpixel(x,y,color); } } } else if(k>-1) { d=-dx-2*dy; incrE=-2*dy; incrNE=-2*(dx+dy); x=x0,y=y0; putpixel(x,y,color); while(x<x1) { if(d<0) d+=incrE; else { d+=incrNE; y--; } x++; putpixel(x,y,color); } } else { d=2*dx-dy; incrE=-2*dx; incrNE=-2*(dx+dy); x=x0,y=y0; putpixel(x,y,color); while(y>y1) { if(d>0) d+=incrE; else { d+=incrNE; x++; } y--; putpixel(x,y,color); } } } else { x=x0;y=y0; if(y1>y0) while(x<y1) { putpixel(x,y,color); y++; } else while(x>y1) { putpixel(x,y,color); y--; } } } void main() { int gdrive=DETECT, gmode=0,xa,xb,ya,yb; initgraph(&gdrive, &gmode, "d:\\tc"); setbkcolor(BLACK); MidPointLine(300, 20, 20, 350, WHITE); printf("please close it with 'ESC' "); while(getch()!=ESC); closegraph(); }