caption: a to b conversion in subclasss in the following stages
exif: {"Image DocumentName": "Add/Subtract Logic S<= A+B when Sub=\u20180\u2019 else A-B;", "Image ImageDescription": "Convert B to Two\u2019s Complement when Sub=1.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}