Collection of images in Web use reporting system

摘要

A checksum is extracted from an image downloaded to a content recipient. The content recipient transmits the extracted checksum to a data collection site. The data collection site compares the received checksum to a reference checksum. If the received checksum and the reference checksum match, the data collection site uses an image corresponding to the reference checksum as the downloaded image. If the received checksum and the reference checksum do not match, the data collection site retrieves the down-loaded image from the content recipient.