Two examples of php drawing circles. Usage of php drawing functions imagearc() and ImagePng()

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

     $im = ImageCreate (150, 150);
     $grey = ImageColorAllocate ($im, 230, 230, 230);
     $black = ImageColorAllocate ($im, 0, 0, 0);

     ImageString($im, 3, 5, 5, "Figure 18.5: Circle", $black);
     ImageArc($im, 75, 75, 50, 50, 0, 360, $black);
     ImagePng ($im);
     ImageDestroy ($im);
?>

例2，绘制圆形 Drawing a Circle with imagearc()

header("Content-type: image/png");
$image = imagecreate( 200, 200 );
$red = imagecolorallocate($image, 255,0,0);
$blue = imagecolorallocate($image, 0,0,255 );
imagearc( $image, 99, 99, 180, 180, 0, 360, $blue );
imagefill( $image, 99, 99, $blue );
imagepng($image);
?>