function divide_image($imgPath, $x, $y) {
	$path = pathinfo($imgPath);
	$imgDir  = $path['dirname'];
	$imgExt  = '.'.$path['extension'];
	$imgName = $path['filename'];

	if (!file_exists($imgDir.'/'.$imgName.'_C0'.$imgExt)) {
		$CI =& get_instance();
		$CI->load->library('image_lib');

		$size = getimagesize($imgPath);

		$cw = $size[0];
		$ch = $size[1] / $y;
		
		$pw = $cw / $x;
		$ph = $ch;

		$p = 1;
		for ($i=0; $i<$y; $i++) {
			$imgCrop = $imgDir.'/'.$imgName.'_C'.$i.$imgExt;
			$config = array(
				'source_image'	 => $imgPath,
				'new_image'		 => $imgCrop,
				'create_thumb'	 => true,
				'thumb_marker'	 => false,
				'maintain_ratio' => false,
				'width'			 => $cw,
				'height'		 => $ch,
				'x_axis'		 => 0,
				'y_axis'		 => $i * $ch
			);
			$CI->image_lib->initialize($config);
			if ($CI->image_lib->crop()) {
				for ($j=0; $j<$x; $j++) {
					$config = array(
						'source_image'	 => $imgCrop,
						'new_image'		 => $imgDir.'/'.$imgName.'_P'.$p.$imgExt,
						'create_thumb'	 => true,
						'thumb_marker'	 => false,
						'maintain_ratio' => false,
						'width'			 => $pw,
						'height'		 => $ph,
						'x_axis'		 => $j * $pw,
						'y_axis'		 => 0
					);
					$CI->image_lib->initialize($config); 
					$CI->image_lib->crop();
					$p++;
				}
			}
		}
	}

	$imgDir = str_replace(DATA_PATH, DATA_DIR, $imgDir);

	$pcount = $x * $y;
	$plist = array();
	for ($i=1; $i<=$pcount; $i++) {
		$plist[$i]->img = $imgDir.'/'.$imgName.'_P'.$i.$imgExt;
		$plist[$i]->key = $i;
	}

	return $plist;
}

divide_image(DATA_PATH.'/image.jpg', 3, 6);

- 상수소개 
DATA_PATH = $_SERVER['DOCUMENT_ROOT'];
DATA_DIR = '/';

- 예제
1) http://www.tested.co.kr 메인페이지 배경
2) http://www.tested.co.kr/exper/puzzle