从codeigniter加载的视图生成图像

I want to generate an image from my existing codeigniters view. I use codeigniter 3.
This is my code:

$invoice = $this->load->view('member/purchase_invoice',$data,true);

I want to make an image file from $invoice, then save to server directory, so users can download it. I use the generated image to make click to download button, so I don't want to display it.

It solved by using PhantomMagick (github.com/anam-hossain/phantommagick)