You have heard that you can not post your affiliate links on various types of social media such as Facebook, Tumblr, Twitter according to their spam policy. So, if you convert the product image with QR code then it may easier to promote your product where user can reach to your product by scanning your product's QR code.
It is just two steps process. First of all you put your product's link to generate QR code then click next and you will get all preview images with QR code.
Happy AliExpress Affiliate Markeintg