Bresenham's Line Drawing Algorithm -


i made code. code handles case when dx , dy greater 0. do, when 1 of them less 0. algorithm says m should taken absolute , x , y should decremented. how decrement i(x) in second loop?

#include <stdio.h> #include <math.h> #include <conio.h> #include <graphics.h>  void illuminate (int x, int y,  int col) {     putpixel(x+320,240-y,col); }   void main (void) {     int i,x1,y1,x2,y2,j;     float dx,dy,m,e;     int gdriver=detect,gmode;      initgraph(&gdriver,&gmode, "c:\\turboc3\\bgi");     printf("\nenter coordinates of initial point\n");     scanf("%d%d",&x1,&y1);     printf("\nenter coordinates of final point\n");     scanf("%d%d",&x2,&y2);      dx = x2 - x1;     dy = y2 - y1;     m = abs(dy)/abs(dx);     j = y1;     e = m - 1;      line(320,0,320,480);     line(0,240,640,240);      if ( dx >= 0 && dy >= 0 )        {         (i=x1;i<x2-1;i++)         {             illuminate(i,j,4);             if ( e>= 0 )             {                 j = j+1;                 e = e-1.0;             }             e = e+m;         }     }     else     {         (i=x1;i<x2-1;i++)         {             illuminate(i,j,4);             if (e>=0)             {                 j = j-1;                 e = e-1.0;             }             e = e+m;         }     }     getch(); }

one easy way handle case "draw" mirror image of line respect x axis in container , mirror again. don't have way of thinking may figure our should put negation. code in case when dx positive or negative similar , differs @ few signs.


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