Display Loading Image While Page Loads

Hello,
I've a challenge,

I've a view which display student's report card but it takes long to go through all calculations 
and returning the results.

so i'd like to display Loading Image While Page Loads "ExamReport",

PHP Code:

public function getExamReport()
    {
//code........................
echo $this->load->view('report/exam/ExamReport', $this->data, true);
} 


 how can i do it.....