Image Resize doesn't work if the image is too big

[eluser]megabyte[/eluser]
here's the code I'm using.

Code:

function _upload_image(){
        if(!empty($_FILES))
        {
        $this->load->library('upload');
        $this->load->library('image_lib');

                $config['upload_path'] = './photos/';
                $config['allowed_types'] = 'jpg|jpeg|gif|avi';
                $config['encrypt_name'] = 'TRUE';
                $this->upload->initialize($config);
                
                $this->upload->do_upload();
                $resarr = $this->upload->data();
                $file = $resarr['file_name'];
                $this->setMemoryForImage($resarr['full_path']);
                
                if($file != '')
                {
          
                $config['image_library'] = 'GD2';
                //$config['create_thumb'] = TRUE;
                $config['source_image'] = $resarr['full_path'];
                $config['maintain_ratio'] = TRUE;
                $config['width'] = 800;
                $config['height'] = 800;
                $config['master_dim'] = 'width';
                
                $this->image_lib->initialize($config);
                        
                $this->image_lib->resize();
                        
                echo $this->image_lib->display_errors();
                    
                }
                echo $this->upload->display_errors();
            
            //print_r($resarr);        
        }
    }


function setMemoryForImage( $filename ){
    $imageInfo = getimagesize($filename);
    $memoryLimitMB = 0;
    $MB = 1048576;  // number of bytes in 1M
    $K64 = 65536;    // number of bytes in 64K
    $TWEAKFACTOR = 8;  // Or whatever works for you
    $memoryNeeded = round( ( $imageInfo[0] * $imageInfo[1]
                                           * $imageInfo['bits']
                                           * $imageInfo['channels'] / 8
                             + $K64
                           ) * $TWEAKFACTOR
                         );
    //ini_get('memory_limit') only works if compiled with "--enable-memory-limit" also
    //Default memory limit is 8MB so well stick with that.
    //To find out what yours is, view your php.ini file.
    $memoryLimit = 8 * $MB;
    if (function_exists('memory_get_usage') &&
        memory_get_usage() + $memoryNeeded > $memoryLimit)
    {
        $newLimit = $memoryLimitMB + ceil( ( memory_get_usage()
                                            + $memoryNeeded
                                            - $memoryLimit
                                            ) / $MB
                                        );
        ini_set( 'memory_limit', $newLimit . 'M' );
        return true;
    }
    else{
        return false;
    }
}

I hope this helps out others like its helped out me.