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C CODE

Specialty Definition: Bresenham's line algorithm C code

(From Wikipedia, the free Encyclopedia)

An example of Bresenham's line algorithm in C follows. The plotting function is not shown.

void drawline2d(int x0, int y0, int x1, int y1, int color)
{
       int i;
       int steep = 1;
       int sx, sy;  /* step positive or negative (1 or -1) */
       int dx, dy;  /* delta (difference in X and Y between points) */
       int e;

       /*
        * inline swap. On some architectures, the XOR trick may be faster
        */
       int tmpswap;
#define SWAP(a,b) tmpswap = a; a = b; b = tmpswap;

       /*
        * optimize for vertical and horizontal lines here
        */
      
       dx = abs(x1 - x0);
       sx = ((x1 - x0) > 0) ? 1 : -1;
       dy = abs(y1 - y0);
       sy = ((y1 - y0) > 0) ? 1 : -1;
       if (dy > dx) {
               steep = 0;
               SWAP(x0, y0);
               SWAP(dx, dy);
               SWAP(sx, sy);
       }
       e = (dy << 1) - dx;
       for (i = 0; i < dx; i++) {
               if (steep) {
                       plot(x0,y0,color);
               } else {
                       plot(y0,x0,color);
               }
               while (e >= 0) {
                       y0 += sy;
                       e -= (dx << 1);
               }
               x0 += sx;
               e += (dy << 1);
       }
}
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Bresenham's line algorithm C code."

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