When I write this post    https://emby.media/community/index.php?/topic/62382-can-i-customize-picture%E2%80%99s-maxwidth-and-quality/   I realized those links doesn't include any........  token?  or something for verification.   Then I did some test and I found I can view and download my Emby‘s picture without login, just need change the number behind "Items/".   Here is the link,        your.domain/emby/Items/*****/Images/Primary    You can do the test by yourself.