I am also now getting this error. I have tried both options and the component has write to folder and the image is created. the options in image path also show same error except for "Relative Path" which shows a blank page.
I have noticed that the error does duplicate part of the url
Relative path
TCPDF ERROR: [Image] Unable to get image: /usr/local/pem/vhosts/228968/webspace/httpdocs//usr/local/pem/vhosts/228968/webspace/httpdocs/components/com_vmeticket/assets/ean_codes/226935855.jpg
Absolute path
TCPDF ERROR: [Image] Unable to get image:
www.comedyclubs.ie/http://www.comedyclub..._codes/111152844.jpg