Shortlist 3 tools for matching finished website to design

We need a shortlist of 3 tools, whether downloadable software or online - which allow our front end developers to compare a PSD or a JPEG mockup of a web page, to the finally developed page - to do an automated check of whether our implementation and development matches the brief/designs provided to us precisely. We need to develop 'pixel perfect' sites from mockups/designs that we are provided - so the selected tool will save us significant testing and review time. It MUST support multi-browser testing from IE7 upward, Firefox and Safari.