A 640 by 480 synthetic PNG with three asymmetric geometric shapes was horizontally mirrored using Pillow. Both were opened in current production snapshot in Chrome 156.0.8078.74, Clean Outline and A4, and real PNG downloads saved. Output 3508 by 2480; the first output was mirrored horizontally and compared per RGB pixel with the second. 1220 of 8699840 pixel positions differed by at least one channel. See measurements.json, inputs and full outputs. App SHA256 fb728a912378c8e7350a98bbbe3b656a5da1c96955411e3c3ec9e83b30dea13c. Not a photograph or physical print.