In reference to the patent: US6490534
Would a camera-based system that took photographs of the user, but determined the user's measurements through another method( still analyzing the photos of the user) infringe on this patent?
If your measurement technique doesn't implement each and every step mentioned in at least one claim, then you don't infringe this patent. The independent claims of this patent are very detailed, consisting of many steps so I think there is likely significant room to implement alternative solutions. You do have to be aware that there could be other patents that also need to be avoided. Start searching for those by looking at the cited prior art from the patent and patents that cite this one. Also, this patent is listed as lapsed, so it may not an issue in any case, but I'd rather one or the attorneys who lurk here comment on that.