Codeigniter - Multiple Resize Image not working

I've tried on clearing, un-setting the config for resizing the orignal image to different dimensions, but no avail, Under is my current controller code. upload_news_images() is called when user selects images (Orignal images are uploaded, thumbs are created which are shown to user: (using AJAX). When user hits submit form, I've to resize each image using resize() funtions using different dimensions, no error are being displayed.

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class DataHandler extends CI_Controller {
  public function insert_news(){

     // uploaded images array
      $uploaded_images = $this->input->post('uploads');

      // move images
        foreach($uploaded_images as $img){
          $j = 0;
            for($k=0; $k<3; $k++){
             if($k==0){
                $this->resize($img, 176, 176);
             }
             if($k==1){
                $this->resize($img, 360, 360);
             }
             if($k==2){
                $this->resize($img, 1024, 1024);
             }
            }
         //rename("./uploads/tmp/orignals/".$img, "./uploads/images/news/orignals/".$img);
      }     

    exit;

        // WE INSERT NEWS DATA SECOND
        $this->load->model("News_model");
        $news = new News_model();

        $news->title = $this->input->post('title');
        $news->short_desc = $this->input->post('short_desc');
        $news->desc = $this->input->post('description');
        $news->pub_date = date("Y/m/d H:i:s");
        $news->active = $this->input->post('active');

        $tr_id = $this->input->post('tr_id');
        if($tr_id == ""){
            $news->tr_id = NULL;
        }else{
            $news->tr_id = $this->input->post('tr_id');
        }


        $sp_id = $this->input->post('sp_id');
        if($sp_id == ""){
            $news->sp_id = NULL;
        }else{
            $news->sp_id = $this->input->post('sp_id');
        }


        $pl_id = $this->input->post('pl_id');
        if($pl_id == ""){
            $news->pl_id = NULL;
        }else{
            $news->pl_id = $this->input->post('pl_id');
        }

        $city_id = $this->input->post('city_id');
        if($city_id == ""){
            $news->city_id = NULL;
        }else{
            $news->city_id = $this->input->post('city_id');
        }
        $news->save();

        $this->session->set_flashdata('i', 1);
        redirect(SITE_BASE_URL.'admin/addnews');
  }

  public function upload_news_images() {
    $id=$this->generateRandomString();

    $source_image = $_FILES['file']['tmp_name'];
    $source_name = $_FILES['file']['name'];


    $file_extension = pathinfo($source_name,PATHINFO_EXTENSION);
     //echo AAPPATH;exit;
    $tmp_upload_path = "./uploads/tmp/orignals/";
    $tmp_upload_thumb_path = "./uploads/tmp/thumbs/";

    $new_source = $tmp_upload_path.$id.".".$file_extension;
    $new_thumb = $tmp_upload_thumb_path.$id.".".$file_extension;


    if(file_exists($tmp_upload_path.$source_name)){
      unlink($tmp_upload_path.$source_name); //remove the file
    }

    move_uploaded_file($source_image , $new_source);

    $upload_img_arr[] = $new_source;
    $upload_img_data = array("upload_img_arr"=>$upload_img_arr);
    //$this->session->set_userdata($upload_img_data);

    $config['image_library'] = 'gd2';
    $config['source_image'] = $new_source;
    $config['new_image'] = $new_thumb;
    $config['file_permissions'] = 0644;
    $config['create_thumb'] = FALSE;
    $config['maintain_ratio'] = TRUE;
    $config['width'] = 76;
    $config['height'] = 76;
    $this->load->library('image_lib', $config);
    $this->image_lib->initialize();
    $this->image_lib->resize();
    $this->image_lib->clear(); 
    unset($config);
    if (!$this->image_lib->resize()) {
      echo $this->image_lib->display_errors();
    }

    $response = array();
    $response['id'] = $id;
    $response['thumb_url'] = $new_thumb;
    echo json_encode($response);
  }

  function generateRandomString($length = 63) {
    $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $charactersLength = strlen($characters);
    $randomString = '';
    for ($i = 0; $i < $length; $i++) {
        $randomString .= $characters[rand(0, $charactersLength - 1)];
    }
    return $randomString;
}




  function resize($img, $width=0, $height=0){
    $config['image_library'] = 'gd2';
    $config['source_image'] = "./uploads/tmp/orignals/".$img;
    if($width==176){
        $config['new_image'] = "./uploads/images/news/smalls/".$img;
    }else if($width==360){
        $config['new_image'] = "./uploads/images/news/mediums/".$img;
    }else if($width==1024){
        $config['new_image'] = "./uploads/images/news/large/".$img;
    }
    echo $config['new_image']."<br>";
    $config['file_permissions'] = 0644;
    $config['create_thumb'] = FALSE;
    $config['maintain_ratio'] = TRUE;
    $config['width'] = $width;
    $config['height'] = $height;
    $this->load->library('image_lib', $config);
    $this->image_lib->initialize();
    $this->image_lib->resize();
    $this->image_lib->clear(); 
    unset($config);
     if (!$this->image_lib->resize()) {
      echo $this->image_lib->display_errors();
    }
  }  
}