GDLib buede linjer

<?php
header ("Content-type: image/png");

$T1 = 20;
$T2 = 30;

$myImage = @imagecreatetruecolor(640, 480)
      or die("Cannot Initialize new GD image stream");
$text_color = imagecolorallocate($myImage, 255, 255, 224);
$poly_color = imagecolorallocate($myImage, 124, 120, 224);

//calculate x-value and y-value point by point
$points = array();
for ($i=0; $i<1000; $i=$i+1)
{
    //define curve's function
    $x = 310*cos($i/$T1); //define x-value
    $y = 230*sin($i/$T2);//define y-value
   
    //move the coordinate, append a point's x-value and y-value
    $points[] = 320+$x; //x-value
    $points[] = 240-$y;  //y-value
}

//count points
$totalPoints = count($points)/2;

//drawing title
$title = "Final Plot ($totalPoints points)";
imagestring($myImage, 3, 5, 5,  $title, $text_color);

/** drawing points one by one, notice if there
* are 10 points, we need to draw 9 lines:
* 1) point 0 to 1;
* 2) point 1 to 2;
* ...
* ...
* 9) point 8 to 9;
*/
for ($i=0; $i<$totalPoints-1; $i++)
{
    imageLine($myImage, $points[2*$i], $points[1+2*$i], $points[2+2*$i], $points[3+2*$i], $poly_color);   
}

//finalizing
imagepng($myImage);
imagedestroy($myImage);
?>