Drawing lines

[Setain]

I've been working on a map generator for an online game. I have almost everything worked out, except, when I increase the zoom on the image some of the lines aren't drawn. I have a feeling it has to do with my formula, but I might not be using imageline() right either.

My code:

          if($cont)
	 {
	   $sx = $cx - $w/(2*$z);
	   $ex = $cx + $w/(2*$z);
	   for ($i = $sx; $i < $ex; $i++)
	   {
	     if($i % 100 == 0)
	     {
		imageline($im, $i*$z-$sx, 0, $i*$z-$sx, $h-1,$black);
	     }
	   }
	   $sy = $cy - $h/(2*$z);
	   $ey = $cy + $h/(2*$z);
            for ($i = $sy; $i < $ey; $i++)
	   {
	     if($i % 100 == 0)
	     {
	       imageline($im, 0,$i*$z-$sy, $w-1, $i*$z-$sy, $black);
	     }
	   }
	 }

$z is the zoom of the image and $i has no significance. $cx and $cy are the cords of the center of the map. Being that the map is 1000x1000, the default height and width of the image is 1000x1000.

I honestly don't see what I am doing wrong. Can I get any suggestions?

[Installer]

I'm not sure in exactly which place (or places 🙂 ) your arithmetic is wrong, but it's definitely a lot more complicated than it needs to be. I think this will do what you want:

if ($cont) { 
    $step = 100 * $z;
    for ($x = ($cx % $step); $x < $w; $x += $step) { 
        imageline($im, $x, 0, $x, $h, $black); 
    } 
    for ($y = ($cy % $step); $y < $w; $y += $step) { 
        imageline($im, 0, $y, $w, $y, $black); 
    } 
}

[Setain]

Thank you, that fixed my problem.

Unfortunately, now I've a new one.
For the very last function, the map is to be divided into 8 companies. The companies divided by 4 lines. Well, being that the map can be zoomed in on, I need a way have the lines drawn relatively, and I can't even figure out a basic concept of how that would be done. So, would anyone have any suggestions about how I could draw all 4 lines so that they would be in the same place on the map no matter when the center is set to?