How to add image to header in wkhtmltopdf using pdfkit?

Question

I am new to wkhtmltopdf. I am searching on web since last 3-4 hours but got nothing. How can I add image to header.I am doing this by using pdfkit , python 3.6 I tried this

import pdfkit as pk

options = {
    'header-center': 'Header',
    'header-html': '<img src="logo.png" />',
}

pk.from_file('indexref.html',
             'wkhtml2pdf doc test.pdf', options=options)

after doing this I am getting black PDF . Thanks!