rotate large images not working

[eluser]pinarella[/eluser]
i have a problem in codeigniter when rotating large images...bigger than 1.2mb. for smaller images, there is no problem. is there any solution?

here is the code:

Code:

public function rotate(){
    $path = $this->input->post('path');
    $file = $this->input->post('file');
    $config['image_library'] = 'gd2';
    $config['source_image'] = $path;
    $config['rotation_angle'] = '90';
    $config['new_image'] = './uploads/_rot'.$file;
    $this->load->library('image_lib');

    $this->image_lib->initialize($config);
    //$this->image_lib->rotate();
    if(!$this->image_lib->rotate()){
        echo $this->image_lib->display_errors();
    } else {
        echo 'OK';
    }
}