So based on your code, that is telling you that the file doesn't exist (i.e. PHP can't find the image file using the path and/or image name you have provided).
Not sure what website.ca is meant to be referencing in your file path, if your images folder is in your website root, then why not change the path to be
and see if that works.
Also just echo out the $image_name on your page (within your function, before your if(file_exists) statement and make sure that you are getting the correct information.