[Plugin: WordPress HTTPS (SSL)] 1 image my logo not secure, is in my site

Hi
I am setting just some pages to secure. I am using woocommerce. I have set checkout to secure. I checked in googles Consol. Just one image showed a problem. My logo which comes up as http. I thought all images from within my own site should be regarded as secure?
Do I need to make the whole site secure? Is there a downside to that?
Try adding something to my cart here

http://ww.wp.xz.cn/extend/plugins/wordpress-https/