It's unlikely they'd use a logo, because of the brittleness of the technique (ie, it relies on sending 304 Not Modified response due to the absence of the special tracking cookie, not due to the actual cache status).
Also, it's not clear if you get access to the actual binary data from the image as it is served, or new data generated from the image as it is displayed - hence my question as to if using the metadata would work.
Comments
It's unlikely they'd use a logo, because of the brittleness of the technique (ie, it relies on sending 304 Not Modified response due to the absence of the special tracking cookie, not due to the actual cache status).
Also, it's not clear if you get access to the actual binary data from the image as it is served, or new data generated from the image as it is displayed - hence my question as to if using the metadata would work.